Math.Round Math.Round Math.Round Math.Round Method

Definition

Rounds a value to the nearest integer or to the specified number of fractional digits.

Overloads

Round(Decimal, Int32, MidpointRounding) Round(Decimal, Int32, MidpointRounding) Round(Decimal, Int32, MidpointRounding) Round(Decimal, Int32, MidpointRounding)

Rounds a decimal value to a specified number of fractional digits. A parameter specifies how to round the value if it is midway between two numbers.

Round(Double, Int32, MidpointRounding) Round(Double, Int32, MidpointRounding) Round(Double, Int32, MidpointRounding) Round(Double, Int32, MidpointRounding)

Rounds a double-precision floating-point value to a specified number of fractional digits. A parameter specifies how to round the value if it is midway between two numbers.

Round(Double, MidpointRounding) Round(Double, MidpointRounding) Round(Double, MidpointRounding) Round(Double, MidpointRounding)

Rounds a double-precision floating-point value to the nearest integer. A parameter specifies how to round the value if it is midway between two numbers.

Round(Double, Int32) Round(Double, Int32) Round(Double, Int32) Round(Double, Int32)

Rounds a double-precision floating-point value to a specified number of fractional digits.

Round(Double) Round(Double) Round(Double) Round(Double)

Rounds a double-precision floating-point value to the nearest integral value.

Round(Decimal, Int32) Round(Decimal, Int32) Round(Decimal, Int32) Round(Decimal, Int32)

Rounds a decimal value to a specified number of fractional digits.

Round(Decimal) Round(Decimal) Round(Decimal) Round(Decimal)

Rounds a decimal value to the nearest integral value.

Round(Decimal, MidpointRounding) Round(Decimal, MidpointRounding) Round(Decimal, MidpointRounding) Round(Decimal, MidpointRounding)

Rounds a decimal value to the nearest integer. A parameter specifies how to round the value if it is midway between two numbers.

Remarks

In this section:

Overloaded method syntax
Parameters
Return value
Exceptions
Which method do I call?
Midpoint values and rounding conventions
Rounding and precision
Rounding and single-precision floating-point values
Examples:
Math.Round(Decimal)
Math.Round(Double)
Math.Round(Decimal, Int32)
Math.Round(Decimal, MidpointRounding)
Math.Round(Double, Int32)
Math.Round(Double, MidpointRounding)
Math.Round(Decimal, Int32, MidpointRounding)
Math.Round(Double, Int32, MidpointRounding)
Version information

Overloaded method syntax

For additional guidance on choosing an overload, see Which method do I call?

Decimal Math.Round(Decimal d )
Rounds a decimal value to the nearest integer, and rounds midpoint values to the nearest even number (example).

Double Math.Round(Double a )
Rounds a double-precision floating-point value to the nearest integer, and rounds midpoint values to the nearest even number (example).

Decimal Math.Round(Decimal d , Int32 decimals )
Rounds a decimal value to a specified number of fractional digits, and rounds midpoint values to the nearest even number (example).

Double Math.Round(Double value , Int32 digits )
Rounds a double-precision floating-point value to a specified number of fractional digits, and rounds midpoint values to the nearest even number (example).

Decimal Math.Round(Decimal d , MidpointRounding mode )
Rounds a decimal value to the nearest integer, and uses the specified rounding convention for midpoint values (example).

Double Math.Round(Double value , MidpointRounding mode )
Rounds a double-precision floating-point value to the nearest integer, and uses the specified rounding convention for midpoint values (example).

Decimal Math.Round(Decimal d , Int32 decimals , MidpointRounding mode )
Rounds a decimal value to a specified number of fractional digits, and uses the specified rounding convention for midpoint values (example).

Double Math.Round(Double value , Int32 digits , MidpointRounding mode )
Rounds a double-precision floating-point value to a specified number of fractional digits, and uses the specified rounding convention for midpoint values (example).

Parameters

This is a complete list of parameters for the Round method. For the parameters used by each overload, see the overload syntax above.

Parameter Type Description
d Decimal A number to be rounded.
a

-or-

value
Double A double-precision floating-point number to be rounded.
decimals

-or-

digits
Int32 The number of fractional digits in the return value. For Decimal values, it can range from 0 to 28. For Double values, it can range from 0 to 15. Note that 15 is the maximum number of integral and fractional digits supported by the Double type.

Default value: 0, which rounds to an integer
mode MidpointRounding A flag that specifies the convention to use for rounding midpoint values. See Midpoint values and rounding conventions.

Default value: MidpointRounding.ToEven

Return value

Type: Decimal or Double, depending on the type of the value to be rounded.
A numeric value of the same type as d, a, or value, but rounded either to an integer or to the specified number of decimal digits. See Midpoint values and rounding conventions for information about rounding numbers with midpoint values.

Warning

When rounding midpoint values, the rounding algorithm performs an equality test. Because of problems of binary representation and precision in the floating-point format, the value returned by the method can be unexpected. For more information, see Rounding and precision.

If an overload with a Double parameter is called with Double.NaN, the method returns Double.NaN. If it is called with Double.PositiveInfinity or Double.NegativeInfinity, the method returns Double.PositiveInfinity or Double.NegativeInfinity, respectively.

Exceptions

Exception Condition Thrown by
OverflowException The result is outside the range of the Decimal type. Round(Decimal)

Round(Decimal, Int32)

Round(Decimal, MidpointRounding)

Round(Decimal, Int32, MidpointRounding)
ArgumentOutOfRangeException decimals is less than 0 or greater than 28.

-or-

digits is less than 0 or greater than 15.
Round(Decimal, Int32)

Round(Double, Int32)

Round(Decimal, Int32, MidpointRounding)

Round(Double, Int32, MidpointRounding)
ArgumentException mode is not a valid value of MidpointRounding. Round(Decimal, MidpointRounding)

Round(Double, MidpointRounding)

Round(Decimal, Int32, MidpointRounding)

Round(Double, Int32, MidpointRounding)

Which method do I call?

To Call
Round a number to an integer by using the rounding to nearest convention. Round(Decimal)

-or-

Round(Double)
Round a number to an integer by using a specified rounding convention. Round(Decimal, MidpointRounding)

-or-

Round(Double, MidpointRounding)
Round a number to a specified number of fractional digits by using the rounding to nearest convention. Round(Decimal, Int32)

-or-

Round(Double, Int32)
Round a number to a specified number of fractional digits by using a specified rounding convention. Round(Decimal, Int32, MidpointRounding)

-or-

Round(Double, Int32, MidpointRounding)
Round a Single value to a specified number of fractional digits by using a specified rounding convention and minimizing the loss of precision. Convert the Single to a Decimal and call Round(Decimal, Int32, MidpointRounding).
Round a number to a specified number of fractional digits while minimizing problems of precision in rounding midpoint values. Call a rounding method that implements a "greater than or approximately equal to" comparison. See Rounding and precision.
Round a fractional value to an integer that is greater than the fractional value. For example, round 3.1 to 4. Ceiling
Round a fractional value to an integer that is less than the fractional value. For example, round 3.9 to 3. Floor

Midpoint values and rounding conventions

Rounding involves converting a numeric value with a specified precision to the nearest value with less precision. For example, you can use the Round(Double) method to round a value of 3.4 to 3.0, and the Round(Double, Int32) method to round a value of 3.579 to 3.58.

In a midpoint value, the value after the least significant digit in the result is precisely half way between two numbers. For example, 3.47500 is a midpoint value if it is to be rounded two decimal places, and 7.500 is a midpoint value if it is to be rounded to an integer. In these cases, the nearest value can't be easily identified without a rounding convention.

The Round method supports two rounding conventions for handling midpoint values:

Rounding away from zero
Midpoint values are rounded to the next number away from zero. For example, 3.75 rounds to 3.8, 3.85 rounds to 3.9, -3.75 rounds to -3.8, and -3.85 rounds to -3.9. This form of rounding is represented by the MidpointRounding.AwayFromZero enumeration member.

Rounding away from zero is the most widely known form of rounding.

Rounding to nearest, or banker's rounding
Midpoint values are rounded to the nearest even number. For example, both 3.75 and 3.85 round to 3.8, and both -3.75 and -3.85 round to -3.8. This form of rounding is represented by the MidpointRounding.ToEven enumeration member.

Rounding to nearest is the standard form of rounding used in financial and statistical operations. It conforms to IEEE Standard 754, section 4. When used in multiple rounding operations, it reduces the rounding error that is caused by consistently rounding midpoint values in a single direction. In some cases, this rounding error can be significant.

The following example illustrates the bias that can result from consistently rounding midpoint values in a single direction. The example computes the true mean of an array of Decimal values, and then computes the mean when the values in the array are rounded by using the two conventions. In this example, the true mean and the mean that results when rounding to nearest are the same. However, the mean that results when rounding away from zero differs by .05 (or by 3.6%) from the true mean.

using System;

public class Example
{
   public static void Main()
   {
      decimal[] values = { 1.15m, 1.25m, 1.35m, 1.45m, 1.55m, 1.65m };
      decimal sum = 0;
      
      // Calculate true mean.
      foreach (var value in values)
         sum += value;

      Console.WriteLine("True mean:     {0:N2}", sum/values.Length);
      
      // Calculate mean with rounding away from zero.
      sum = 0;
      foreach (var value in values)
         sum += Math.Round(value, 1, MidpointRounding.AwayFromZero);

      Console.WriteLine("AwayFromZero:  {0:N2}", sum/values.Length);
      
      // Calculate mean with rounding to nearest.
      sum = 0;
      foreach (var value in values)
         sum += Math.Round(value, 1, MidpointRounding.ToEven);

      Console.WriteLine("ToEven:        {0:N2}", sum/values.Length);
   }
}
// The example displays the following output:
//       True mean:     1.40
//       AwayFromZero:  1.45
//       ToEven:        1.40
Module Example
   Public Sub Main()
      Dim values() As Decimal = { 1.15d, 1.25d, 1.35d, 1.45d, 1.55d, 1.65d }
      Dim sum As Decimal
      
      ' Calculate true mean.
      For Each value In values
         sum += value
      Next
      Console.WriteLine("True mean:     {0:N2}", sum/values.Length)
      
      ' Calculate mean with rounding away from zero.
      sum = 0
      For Each value In values
         sum += Math.Round(value, 1, MidpointRounding.AwayFromZero)
      Next
      Console.WriteLine("AwayFromZero:  {0:N2}", sum/values.Length)
      
      ' Calculate mean with rounding to nearest.
      sum = 0
      For Each value In values
         sum += Math.Round(value, 1, MidpointRounding.ToEven)
      Next
      Console.WriteLine("ToEven:        {0:N2}", sum/values.Length)
   End Sub
End Module
' The example displays the following output:
'       True mean:     1.40
'       AwayFromZero:  1.45
'       ToEven:        1.40

By default, the Round method uses the rounding to nearest convention. The following table lists the overloads of the Round method and the rounding convention that each uses.

Overload Rounding convention
Round(Decimal) ToEven
Round(Double) ToEven
Round(Decimal, Int32) ToEven
Round(Double, Int32) ToEven
Round(Decimal, MidpointRounding) Determined by mode parameter.
Round(Double, MidpointRounding) Determined by mode parameter
Round(Decimal, Int32, MidpointRounding) Determined by mode parameter
Round(Double, Int32, MidpointRounding) Determined by mode parameter

Rounding and precision

In order to determine whether a rounding operation involves a midpoint value, the Round method multiplies the original value to be rounded by 10n, where n is the desired number of fractional digits in the return value, and then determines whether the remaining fractional portion of the value is greater than or equal to .5. This is a slight variation on a test for equality, and as discussed in the "Testing for Equality" section of the Double reference topic, tests for equality with floating-point values are problematic because of the floating-point format's issues with binary representation and precision. This means that any fractional portion of a number that is slightly less than .5 (because of a loss of precision) will not be rounded upward.

The following example illustrates the problem. It repeatedly adds .1 to 11.0 and rounds the result to the nearest integer. Regardless of the rounding convention, 11.5 should round to 12. However, as the output from the example shows, it does not. The example uses the "R" standard numeric format string to display the floating point value's full precision, and shows that the value to be rounded has lost precision during repeated additions, and its value is actually 11.499999999999998. Because .499999999999998 is less than .5, the value is not rounded to the next highest integer. As the example also shows, this problem does not occur if we simply assign the constant value 11.5 to a Double variable.

using System;

public class Example
{
   public static void Main()
   {
      Console.WriteLine("{0,5} {1,20:R}  {2,12} {3,15}\n", 
                        "Value", "Full Precision", "ToEven",
                        "AwayFromZero");
      double value = 11.1;
      for (int ctr = 0; ctr <= 5; ctr++)    
         value = RoundValueAndAdd(value);

      Console.WriteLine();

      value = 11.5;
      RoundValueAndAdd(value);
   }
   
   private static double RoundValueAndAdd(double value)
   {
      Console.WriteLine("{0,5:N1} {0,20:R}  {1,12} {2,15}", 
                        value, Math.Round(value, MidpointRounding.ToEven),
                        Math.Round(value, MidpointRounding.AwayFromZero));
      return value + .1;
   }
}
// The example displays the following output:
//       Value       Full Precision        ToEven    AwayFromZero
//       
//        11.1                 11.1            11              11
//        11.2                 11.2            11              11
//        11.3   11.299999999999999            11              11
//        11.4   11.399999999999999            11              11
//        11.5   11.499999999999998            11              11
//        11.6   11.599999999999998            12              12
//       
//        11.5                 11.5            12              12
Module Example
   Public Sub Main()
      Dim value As Double = 11.1

      Console.WriteLine("{0,5} {1,20:R}  {2,12} {3,15}", 
                        "Value", "Full Precision", "ToEven",
                        "AwayFromZero")
      Console.WriteLine()
      For ctr As Integer = 0 To 5    
         value = RoundValueAndAdd(value)
      Next
      Console.WriteLine()

      value = 11.5
      RoundValueAndAdd(value)
   End Sub
   
   Private Function RoundValueAndAdd(value As Double) As Double
      Console.WriteLine("{0,5:N1} {0,20:R}  {1,12} {2,15}", 
                        value, Math.Round(value, MidpointRounding.ToEven),
                        Math.Round(value, MidpointRounding.AwayFromZero))
      Return value + .1
   End Function   
End Module
' The example displays the following output:
'       Value       Full Precision        ToEven    AwayFromZero
'       
'        11.1                 11.1            11              11
'        11.2                 11.2            11              11
'        11.3   11.299999999999999            11              11
'        11.4   11.399999999999999            11              11
'        11.5   11.499999999999998            11              11
'        11.6   11.599999999999998            12              12
'       
'        11.5                 11.5            12              12

Problems of precision in rounding midpoint values are most likely to arise in the following conditions:

  • When a fractional value cannot be expressed precisely in the floating-point type's binary format.

  • When the value to be rounded is calculated from one or more floating-point operations.

  • When the value to be rounded is a Single rather than a Double or Decimal. For more information, see the next section, Rounding and single-precision floating-point values.

In cases where the lack of precision in rounding operations is problematic, you can do the following:

  • If the rounding operation calls an overload that rounds a Double value, you can change the Double to a Decimal value and call an overload that rounds a Decimal value instead. Although the Decimal data type also has problems of representation and loss of precision, these issues are far less common.

  • Define a custom rounding algorithm that performs a "nearly equal" test to determine whether the value to be rounded is acceptably close to a midpoint value. The following example defines a RoundApproximate method that examines whether a fractional value is sufficiently near to a midpoint value to be subject to midpoint rounding. As the output from the example shows, it corrects the rounding problem shown in the previous example.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Console.WriteLine("{0,5} {1,20:R}  {2,12} {3,15}\n", 
                            "Value", "Full Precision", "ToEven",
                            "AwayFromZero");
          double value = 11.1;
          for (int ctr = 0; ctr <= 5; ctr++)    
             value = RoundValueAndAdd(value);
    
          Console.WriteLine();
    
          value = 11.5;
          RoundValueAndAdd(value);
       }
       
       private static double RoundValueAndAdd(double value)
       {
          const double tolerance = 8e-14;
    
          Console.WriteLine("{0,5:N1} {0,20:R}  {1,12} {2,15}", 
                            value, 
                            RoundApproximate(value, 0, tolerance, MidpointRounding.ToEven),
                            RoundApproximate(value, 0, tolerance, MidpointRounding.AwayFromZero));
          return value + .1;
       }
    
       private static double RoundApproximate(double dbl, int digits, double margin, 
                                         MidpointRounding mode)
       {                                      
          double fraction = dbl * Math.Pow(10, digits);
          double value = Math.Truncate(fraction); 
          fraction = fraction - value;   
          if (fraction == 0)
             return dbl;
          
          double tolerance = margin * dbl;
          // Determine whether this is a midpoint value.
          if ((fraction >= .5 - tolerance) & (fraction <= .5 + tolerance)) {
             if (mode == MidpointRounding.AwayFromZero)
                return (value + 1)/Math.Pow(10, digits);
             else
                if (value % 2 != 0)
                   return (value + 1)/Math.Pow(10, digits);
                else
                   return value/Math.Pow(10, digits);
          }
          // Any remaining fractional value greater than .5 is not a midpoint value.
          if (fraction > .5)
             return (value + 1)/Math.Pow(10, digits);
          else
             return value/Math.Pow(10, digits);
       }
    }
    // The example displays the following output:
    //       Value       Full Precision        ToEven    AwayFromZero
    //       
    //        11.1                 11.1            11              11
    //        11.2                 11.2            11              11
    //        11.3   11.299999999999999            11              11
    //        11.4   11.399999999999999            11              11
    //        11.5   11.499999999999998            12              12
    //        11.6   11.599999999999998            12              12
    //       
    //        11.5                 11.5            12              12
    
    Module Example
       Public Sub Main()
          Dim value As Double = 11.1
    
          Console.WriteLine("{0,5} {1,20:R}  {2,12} {3,15}\n", 
                            "Value", "Full Precision", "ToEven",
                            "AwayFromZero")
          For ctr As Integer = 0 To 5    
             value = RoundValueAndAdd(value)
          Next
          Console.WriteLine()
    
          value = 11.5
          RoundValueAndAdd(value)
       End Sub
       
       Private Function RoundValueAndAdd(value As Double) As Double
          Const tolerance As Double = 8e-14
          Console.WriteLine("{0,5:N1} {0,20:R}  {1,12} {2,15}", 
                            value, 
                            RoundApproximate(value, 0, tolerance, MidpointRounding.ToEven),
                            RoundApproximate(value, 0, tolerance, MidpointRounding.AwayFromZero))
          Return value + .1
       End Function   
    
       Private Function RoundApproximate(dbl As Double, digits As Integer, margin As Double, 
                                         mode As MidpointRounding) As Double
          Dim fraction As Double = dbl * Math.Pow(10, digits)
          Dim value As Double = Math.Truncate(fraction) 
          fraction = fraction - value   
          If fraction = 0 Then Return dbl
          
          Dim tolerance As Double = margin * dbl
          ' Determine whether this is a midpoint value.
          If (fraction >= .5 - tolerance) And (fraction <= .5 + tolerance) Then
             If mode = MidpointRounding.AwayFromZero Then
                Return (value + 1)/Math.Pow(10, digits)
             Else
                If value Mod 2 <> 0 Then
                   Return (value + 1)/Math.Pow(10, digits)
                Else
                   Return value/Math.Pow(10, digits)
                End If
             End If
          End If
          ' Any remaining fractional value greater than .5 is not a midpoint value.
          If fraction > .5 Then
             Return (value + 1)/Math.Pow(10, digits)
          Else
             return value/Math.Pow(10, digits)
          End If      
       End Function
    End Module
    ' The example displays the following output:
    '       Value       Full Precision        ToEven    AwayFromZero
    '       
    '        11.1                 11.1            11              11
    '        11.2                 11.2            11              11
    '        11.3   11.299999999999999            11              11
    '        11.4   11.399999999999999            11              11
    '        11.5   11.499999999999998            12              12
    '        11.6   11.599999999999998            12              12
    '       
    '        11.5                 11.5            12              12
    

Rounding and single-precision floating-point values

The Round method includes overloads that accept arguments of type Decimal and Double. There are no methods that round values of type Single. If you pass a Single value to one of the overloads of the Round method, it is cast (in C#) or converted (in Visual Basic) to a Double, and the corresponding Round overload with a Double parameter is called. Although this is a widening conversion, it often involves a loss of precision, as the following example illustrates. When a Single value of 16.325 is passed to the Round method and rounded to two decimal places using the rounding to nearest convention, the result is 16.33 and not the expected result of 16.32.

using System;

public class Example
{
   public static void Main()
   {
      Single value = 16.325f;
      Console.WriteLine("Widening Conversion of {0:R} (type {1}) to {2:R} (type {3}): ", 
                        value, value.GetType().Name, (double) value, 
                        ((double) (value)).GetType().Name);
      Console.WriteLine(Math.Round(value, 2));
      Console.WriteLine(Math.Round(value, 2, MidpointRounding.AwayFromZero));
      Console.WriteLine();
      
      Decimal decValue = (decimal) value;
      Console.WriteLine("Cast of {0:R} (type {1}) to {2} (type {3}): ", 
                        value, value.GetType().Name, decValue, 
                        decValue.GetType().Name);
      Console.WriteLine(Math.Round(decValue, 2));
      Console.WriteLine(Math.Round(decValue, 2, MidpointRounding.AwayFromZero));
   }
}
// The example displays the following output:
//    Widening Conversion of 16.325 (type Single) to 16.325000762939453 (type Double):
//    16.33
//    16.33
//    
//    Cast of 16.325 (type Single) to 16.325 (type Decimal):
//    16.32
//    16.33
Module Example
   Public Sub Main()
      Dim value As Single = 16.325
      Console.WriteLine("Widening Conversion of {0:R} (type {1}) to {2:R} (type {3}): ", 
                        value, value.GetType().Name, CDbl(value), 
                        CDbl(value).GetType().Name)
      Console.WriteLine(Math.Round(value, 2))
      Console.WriteLine(Math.Round(value, 2, MidpointRounding.AwayFromZero))
      Console.WriteLine()
      
      Dim decValue As Decimal = CDec(value)
      Console.WriteLine("Cast of {0:R} (type {1}) to {2} (type {3}): ", 
                        value, value.GetType().Name, decValue, 
                        decValue.GetType().Name)
      Console.WriteLine(Math.Round(decValue, 2))
      Console.WriteLine(Math.Round(decValue, 2, MidpointRounding.AwayFromZero))
      Console.WriteLine()
   End Sub
End Module
' The example displays the following output:
'    Widening Conversion of 16.325 (type Single) to 16.325000762939453 (type Double):
'    16.33
'    16.33
'    
'    Cast of 16.325 (type Single) to 16.325 (type Decimal):
'    16.32
'    16.33

This unexpected result is due to a loss of precision in the conversion of the Single value to a Double. Because the resulting Double value of 16.325000762939453 is not a midpoint value and is greater than 16.325, it is always rounded upward.

In many cases, as the example illustrates, the loss of precision can be minimized or eliminated by casting or converting the Single value to a Decimal. Note that, because this is a narrowing conversion, it requires using a cast operator or calling a conversion method.

Math.Round(Decimal) example

The following example demonstrates the Round(Decimal) method. Note that the Decimal value of 4.5 rounds to 4 rather than 5, because this overload uses the default ToEven convention.

using System;

class Example
{
   static void Main()
   {
      for (decimal value = 4.2m; value <= 4.8m; value+=.1m )
         Console.WriteLine("{0} --> {1}", value, Math.Round(value));
   }
}
// The example displays the following output:
//       4.2 --> 4
//       4.3 --> 4
//       4.4 --> 4
//       4.5 --> 4
//       4.6 --> 5
//       4.7 --> 5
//       4.8 --> 5
Module Example
   Public Sub Main()
      For value As Decimal = 4.2d To 4.8d Step .1d
         Console.WriteLine("{0} --> {1}", value, Math.Round(value))
      Next   
   End Sub                                                                 
End Module
' The example displays the following output:
'       4.2 --> 4
'       4.3 --> 4
'       4.4 --> 4
'       4.5 --> 4
'       4.6 --> 5
'       4.7 --> 5
'       4.8 --> 5

Math.Round(Double) example

The following example demonstrates rounding to the nearest integer value.

using namespace System;

void main()
{
    Console::WriteLine("Classic Math.Round in CPP");
    Console::WriteLine(Math::Round(4.4));     // 4
    Console::WriteLine(Math::Round(4.5));     // 4
    Console::WriteLine(Math::Round(4.6));     // 5
    Console::WriteLine(Math::Round(5.5));     // 6
}
using System;

class Program
{
    static void Main()
    {
    Console.WriteLine("Classic Math.Round in CSharp");
    Console.WriteLine(Math.Round(4.4)); // 4
    Console.WriteLine(Math.Round(4.5)); // 4
    Console.WriteLine(Math.Round(4.6)); // 5
    Console.WriteLine(Math.Round(5.5)); // 6
    }
}
Imports System

Module Module1

    Sub Main()
    Console.WriteLine("Classic Math.Round in Visual Basic")
    Console.WriteLine(Math.Round(4.4)) ' 4
    Console.WriteLine(Math.Round(4.5)) ' 4
    Console.WriteLine(Math.Round(4.6)) ' 5
    Console.WriteLine(Math.Round(5.5)) ' 6
    End Sub

End Module

Math.Round(Decimal, Int32) example

The following example rounds decimal values with two fractional digits to values that have a single fractional digit.

using System;

public class Sample {
   static void Main() {
      Console.WriteLine(Math.Round(3.44m, 1)); 
      Console.WriteLine(Math.Round(3.45m, 1)); 
      Console.WriteLine(Math.Round(3.46m, 1)); 
      Console.WriteLine();
      
      Console.WriteLine(Math.Round(4.34m, 1)); 
      Console.WriteLine(Math.Round(4.35m, 1)); 
      Console.WriteLine(Math.Round(4.36m, 1)); 
   }
}
// The example displays the following output:
//       3.4
//       3.4
//       3.5
//       
//       4.3
//       4.4
//       4.4
Public Module Example
   Sub Main()
      Console.WriteLine(Math.Round(3.44, 1)) 
      Console.WriteLine(Math.Round(3.45, 1)) 
      Console.WriteLine(Math.Round(3.46, 1)) 
      Console.WriteLine()
      
      Console.WriteLine(Math.Round(4.34, 1)) 
      Console.WriteLine(Math.Round(4.35, 1)) 
      Console.WriteLine(Math.Round(4.36, 1)) 
   End Sub  
End Module
' The example displays the following output:
'       3.4
'       3.4
'       3.5
'       
'       4.3
'       4.4
'       4.4

Math.Round(Double, Int32) example

The following example rounds double values with two fractional digits to doubles that have a single fractional digit.

Math::Round(3.44, 1); //Returns 3.4.
Math::Round(3.45, 1); //Returns 3.4.
Math::Round(3.46, 1); //Returns 3.5.

Math::Round(4.34, 1); // Returns 4.3
Math::Round(4.35, 1); // Returns 4.4
Math::Round(4.36, 1); // Returns 4.4
Math.Round(3.44, 1); //Returns 3.4.
Math.Round(3.45, 1); //Returns 3.4.
Math.Round(3.46, 1); //Returns 3.5.

Math.Round(4.34, 1); // Returns 4.3
Math.Round(4.35, 1); // Returns 4.4
Math.Round(4.36, 1); // Returns 4.4
Math.Round(3.44, 1) 'Returns 3.4.
Math.Round(3.45, 1) 'Returns 3.4.
Math.Round(3.46, 1) 'Returns 3.5.

Math.Round(4.34, 1) ' Returns 4.3
Math.Round(4.35, 1) ' Returns 4.4
Math.Round(4.36, 1) ' Returns 4.4

Math.Round(Decimal, MidpointRounding) example

The following example displays values returned by the Round(Decimal) method, the Round(Decimal, MidpointRounding) method with a mode argument of ToEven, and the Round(Decimal, MidpointRounding) method with a mode argument of AwayFromZero.

using System;

public class Example
{
   public static void Main()
   {
      Console.WriteLine("{0,-10} {1,-10} {2,-10} {3,-15}", "Value", "Default", 
                        "ToEven", "AwayFromZero");
      for (decimal value = 12.0m; value <= 13.0m; value += 0.1m)
         Console.WriteLine("{0,-10} {1,-10} {2,-10} {3,-15}",
                           value, Math.Round(value), 
                           Math.Round(value, MidpointRounding.ToEven),
                           Math.Round(value, MidpointRounding.AwayFromZero));
   }
}
// The example displays the following output:
//       Value      Default    ToEven     AwayFromZero
//       12         12         12         12
//       12.1       12         12         12
//       12.2       12         12         12
//       12.3       12         12         12
//       12.4       12         12         12
//       12.5       12         12         13
//       12.6       13         13         13
//       12.7       13         13         13
//       12.8       13         13         13
//       12.9       13         13         13
//       13.0       13         13         13
Module Example
   Public Sub Main()
      Console.WriteLine("{0,-10} {1,-10} {2,-10} {3,-15}", "Value", "Default", 
                        "ToEven", "AwayFromZero")
      For value As Decimal = 12.0d To 13.0d Step .1d
         Console.WriteLine("{0,-10} {1,-10} {2,-10} {3,-15}",
                           value, Math.Round(value), 
                           Math.Round(value, MidpointRounding.ToEven),
                           Math.Round(value, MidpointRounding.AwayFromZero))
      Next
   End Sub
End Module
' The example displays the following output:
'       Value      Default    ToEven     AwayFromZero
'       12         12         12         12
'       12.1       12         12         12
'       12.2       12         12         12
'       12.3       12         12         12
'       12.4       12         12         12
'       12.5       12         12         13
'       12.6       13         13         13
'       12.7       13         13         13
'       12.8       13         13         13
'       12.9       13         13         13
'       13.0       13         13         13

Math.Round(Double, MidpointRounding) example

The following example displays values returned by the Round(Double) method, the Round(Double, MidpointRounding) method with a mode argument of ToEven, and the Round(Double, MidpointRounding) method with a mode argument of AwayFromZero.

using System;

public class Example
{
   public static void Main()
   {
      Double[] values = { 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 
                          12.7, 12.8, 12.9, 13.0 };
      Console.WriteLine("{0,-10} {1,-10} {2,-10} {3,-15}", "Value", "Default", 
                        "ToEven", "AwayFromZero");
      foreach (var value in values)
         Console.WriteLine("{0,-10:R} {1,-10} {2,-10} {3,-15}",
                           value, Math.Round(value), 
                           Math.Round(value, MidpointRounding.ToEven),
                           Math.Round(value, MidpointRounding.AwayFromZero));
   }
}
// The example displays the following output:
//       Value      Default    ToEven     AwayFromZero
//       12         12         12         12
//       12.1       12         12         12
//       12.2       12         12         12
//       12.3       12         12         12
//       12.4       12         12         12
//       12.5       12         12         13
//       12.6       13         13         13
//       12.7       13         13         13
//       12.8       13         13         13
//       12.9       13         13         13
//       13.0       13         13         13
Module Example
   Public Sub Main()
      Dim values() As Double = { 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 
                                 12.7, 12.8, 12.9, 13.0 }
      Console.WriteLine("{0,-10} {1,-10} {2,-10} {3,-15}", "Value", "Default", 
                        "ToEven", "AwayFromZero")
      For Each value In values
         Console.WriteLine("{0,-10} {1,-10} {2,-10} {3,-15}",
                           value, Math.Round(value), 
                           Math.Round(value, MidpointRounding.ToEven),
                           Math.Round(value, MidpointRounding.AwayFromZero))
      Next
   End Sub
End Module
' The example displays the following output:
'       Value      Default    ToEven     AwayFromZero
'       12         12         12         12
'       12.1       12         12         12
'       12.2       12         12         12
'       12.3       12         12         12
'       12.4       12         12         12
'       12.5       12         12         13
'       12.6       13         13         13
'       12.7       13         13         13
'       12.8       13         13         13
'       12.9       13         13         13
'       13.0       13         13         13

Math.Round(Decimal, Int32, MidpointRounding) example

The following example demonstrates how to use the Round method with the MidpointRounding enumeration.

// This example demonstrates the Math.Round() method in conjunction 
// with the MidpointRounding enumeration.
using namespace System;

void main()
{
    Decimal result = (Decimal) 0.0;
    Decimal posValue = (Decimal) 3.45;
    Decimal negValue = (Decimal) -3.45;

    // By default, round a positive and a negative value to the nearest
    // even number. The precision of the result is 1 decimal place.
    result = Math::Round(posValue, 1);
    Console::WriteLine("{0,4} = Math.Round({1,5}, 1)", result, posValue);
    result = Math::Round(negValue, 1);
    Console::WriteLine("{0,4} = Math.Round({1,5}, 1)", result, negValue);
    Console::WriteLine();

    // Round a positive value to the nearest even number, then to the
    // nearest number away from zero. The precision of the result is 1
    // decimal place.
    result = Math::Round(posValue, 1, MidpointRounding::ToEven);
    Console::WriteLine(
        "{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)",
        result, posValue);
    result = Math::Round(posValue, 1, MidpointRounding::AwayFromZero);
    Console::WriteLine(
        "{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)",
        result, posValue);
    Console::WriteLine();

    // Round a negative value to the nearest even number, then to the
    // nearest number away from zero. The precision of the result is 1
    // decimal place.
    result = Math::Round(negValue, 1, MidpointRounding::ToEven);
    Console::WriteLine(
        "{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)",
        result, negValue);
    result = Math::Round(negValue, 1, MidpointRounding::AwayFromZero);
    Console::WriteLine(
        "{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)",
        result, negValue);
    Console::WriteLine();
}

/*
This code example produces the following results:

3.4 = Math.Round( 3.45, 1)
-3.4 = Math.Round(-3.45, 1)

3.4 = Math.Round( 3.45, 1, MidpointRounding.ToEven)
3.5 = Math.Round( 3.45, 1, MidpointRounding.AwayFromZero)

-3.4 = Math.Round(-3.45, 1, MidpointRounding.ToEven)
-3.5 = Math.Round(-3.45, 1, MidpointRounding.AwayFromZero)

*/
// This example demonstrates the Math.Round() method in conjunction 
// with the MidpointRounding enumeration.
using System;

class Sample 
{
    public static void Main() 
    {
    decimal result = 0.0m;
    decimal posValue =  3.45m;
    decimal negValue = -3.45m;

// By default, round a positive and a negative value to the nearest even number. 
// The precision of the result is 1 decimal place.

    result = Math.Round(posValue, 1);
    Console.WriteLine("{0,4} = Math.Round({1,5}, 1)", result, posValue);
    result = Math.Round(negValue, 1);
    Console.WriteLine("{0,4} = Math.Round({1,5}, 1)", result, negValue);
    Console.WriteLine();

// Round a positive value to the nearest even number, then to the nearest number away from zero. 
// The precision of the result is 1 decimal place.

    result = Math.Round(posValue, 1, MidpointRounding.ToEven);
    Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", result, posValue);
    result = Math.Round(posValue, 1, MidpointRounding.AwayFromZero);
    Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)", result, posValue);
    Console.WriteLine();

// Round a negative value to the nearest even number, then to the nearest number away from zero. 
// The precision of the result is 1 decimal place.

    result = Math.Round(negValue, 1, MidpointRounding.ToEven);
    Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", result, negValue);
    result = Math.Round(negValue, 1, MidpointRounding.AwayFromZero);
    Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)", result, negValue);
    Console.WriteLine();
    }
}
/*
This code example produces the following results:

 3.4 = Math.Round( 3.45, 1)
-3.4 = Math.Round(-3.45, 1)

 3.4 = Math.Round( 3.45, 1, MidpointRounding.ToEven)
 3.5 = Math.Round( 3.45, 1, MidpointRounding.AwayFromZero)

-3.4 = Math.Round(-3.45, 1, MidpointRounding.ToEven)
-3.5 = Math.Round(-3.45, 1, MidpointRounding.AwayFromZero)

*/
' This example demonstrates the Math.Round() method in conjunction 
' with the MidpointRounding enumeration.
Imports System

Class Sample
    Public Shared Sub Main() 
        Dim result As Decimal = 0D
        Dim posValue As Decimal = 3.45D
        Dim negValue As Decimal = -3.45D
        
        ' By default, round a positive and a negative value to the nearest even number. 
        ' The precision of the result is 1 decimal place.
        result = Math.Round(posValue, 1)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1)", result, posValue)
        result = Math.Round(negValue, 1)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1)", result, negValue)
        Console.WriteLine()
        
        ' Round a positive value to the nearest even number, then to the nearest number 
        ' away from zero. The precision of the result is 1 decimal place.
        result = Math.Round(posValue, 1, MidpointRounding.ToEven)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", _
                           result, posValue)
        result = Math.Round(posValue, 1, MidpointRounding.AwayFromZero)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)", _
                           result, posValue)
        Console.WriteLine()
        
        ' Round a negative value to the nearest even number, then to the nearest number 
        ' away from zero. The precision of the result is 1 decimal place.
        result = Math.Round(negValue, 1, MidpointRounding.ToEven)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", _
                            result, negValue)
        result = Math.Round(negValue, 1, MidpointRounding.AwayFromZero)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)", _
                           result, negValue)
        Console.WriteLine()
    
    End Sub 'Main
End Class 'Sample
'
'This code example produces the following results:
'
' 3.4 = Math.Round( 3.45, 1)
'-3.4 = Math.Round(-3.45, 1)
'
' 3.4 = Math.Round( 3.45, 1, MidpointRounding.ToEven)
' 3.5 = Math.Round( 3.45, 1, MidpointRounding.AwayFromZero)
'
'-3.4 = Math.Round(-3.45, 1, MidpointRounding.ToEven)
'-3.5 = Math.Round(-3.45, 1, MidpointRounding.AwayFromZero)
'

Math.Round(Double, Int32, MidpointRounding) example

The following example demonstrates how to use the Round(Double, Int32, MidpointRounding) method with the MidpointRounding enumeration.

using System;

class Sample 
{
    public static void Main() 
    {
       double posValue =  3.45;
       double negValue = -3.45;

       // Round a positive and a negative value using the default. 
       double result = Math.Round(posValue, 1);
       Console.WriteLine("{0,4} = Math.Round({1,5}, 1)", result, posValue);
       result = Math.Round(negValue, 1);
       Console.WriteLine("{0,4} = Math.Round({1,5}, 1)\n", result, negValue);

       // Round a positive value using a MidpointRounding value. 
       result = Math.Round(posValue, 1, MidpointRounding.ToEven);
       Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", 
                         result, posValue);
       result = Math.Round(posValue, 1, MidpointRounding.AwayFromZero);
       Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)\n", 
                         result, posValue);

       // Round a negative value using a MidpointRounding value. 
       result = Math.Round(negValue, 1, MidpointRounding.ToEven);
       Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", 
                         result, negValue);
       result = Math.Round(negValue, 1, MidpointRounding.AwayFromZero);
       Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)\n", 
                         result, negValue);
   }
}
// The example displays the following output:
//        3.4 = Math.Round( 3.45, 1)
//       -3.4 = Math.Round(-3.45, 1)
//       
//        3.4 = Math.Round( 3.45, 1, MidpointRounding.ToEven)
//        3.5 = Math.Round( 3.45, 1, MidpointRounding.AwayFromZero)
//       
//       -3.4 = Math.Round(-3.45, 1, MidpointRounding.ToEven)
//       -3.5 = Math.Round(-3.45, 1, MidpointRounding.AwayFromZero)
Module Example
    Public Sub Main() 
        Dim posValue As Double = 3.45
        Dim negValue As Double = -3.45
        
        ' Round a positive and a negative value using the default.  
        Dim result As Double = Math.Round(posValue, 1)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1)", result, posValue)
        result = Math.Round(negValue, 1)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1)", result, negValue)
        Console.WriteLine()
        
        ' Round a positive value using a MidpointRounding value. 
        result = Math.Round(posValue, 1, MidpointRounding.ToEven)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", 
                           result, posValue)
        result = Math.Round(posValue, 1, MidpointRounding.AwayFromZero)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)", 
                           result, posValue)
        Console.WriteLine()
        
        ' Round a positive value using a MidpointRounding value. 
        result = Math.Round(negValue, 1, MidpointRounding.ToEven)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", 
                            result, negValue)
        result = Math.Round(negValue, 1, MidpointRounding.AwayFromZero)
        Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)", 
                           result, negValue)
        Console.WriteLine()
    End Sub
End Module
' The example displays the following output:
'       3.4 = Math.Round( 3.45, 1)
'       -3.4 = Math.Round(-3.45, 1)
'       
'       3.4 = Math.Round( 3.45, 1, MidpointRounding.ToEven)
'       3.5 = Math.Round( 3.45, 1, MidpointRounding.AwayFromZero)
'       
'       -3.4 = Math.Round(-3.45, 1, MidpointRounding.ToEven)
'       -3.5 = Math.Round(-3.45, 1, MidpointRounding.AwayFromZero)

Version information

.NET Framework
Overloads without a MidpointRounding parameter are supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0
Overloads with a MidpointRounding parameter are supported in: 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile
All overloads are supported in: 4, 3.5 SP1

Portable Class Library
All overloads are supported

.NET for Windows Store apps
All overloads are supported in: Windows 8

Round(Decimal, Int32, MidpointRounding) Round(Decimal, Int32, MidpointRounding) Round(Decimal, Int32, MidpointRounding) Round(Decimal, Int32, MidpointRounding)

Rounds a decimal value to a specified number of fractional digits. A parameter specifies how to round the value if it is midway between two numbers.

public:
 static System::Decimal Round(System::Decimal d, int decimals, MidpointRounding mode);
public static decimal Round (decimal d, int decimals, MidpointRounding mode);
static member Round : decimal * int * MidpointRounding -> decimal
Public Shared Function Round (d As Decimal, decimals As Integer, mode As MidpointRounding) As Decimal
Parameters
d
Decimal Decimal Decimal Decimal

A decimal number to be rounded.

decimals
Int32 Int32 Int32 Int32

The number of decimal places in the return value.

mode
MidpointRounding MidpointRounding MidpointRounding MidpointRounding

Specification for how to round d if it is midway between two other numbers.

Returns

The number nearest to d that contains a number of fractional digits equal to decimals. If d has fewer fractional digits than decimals, d is returned unchanged.

Exceptions

Remarks

Note

For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

See Also

Round(Double, Int32, MidpointRounding) Round(Double, Int32, MidpointRounding) Round(Double, Int32, MidpointRounding) Round(Double, Int32, MidpointRounding)

Rounds a double-precision floating-point value to a specified number of fractional digits. A parameter specifies how to round the value if it is midway between two numbers.

public:
 static double Round(double value, int digits, MidpointRounding mode);
public static double Round (double value, int digits, MidpointRounding mode);
static member Round : double * int * MidpointRounding -> double
Public Shared Function Round (value As Double, digits As Integer, mode As MidpointRounding) As Double
Parameters
value
Double Double Double Double

A double-precision floating-point number to be rounded.

digits
Int32 Int32 Int32 Int32

The number of fractional digits in the return value.

mode
MidpointRounding MidpointRounding MidpointRounding MidpointRounding

Specification for how to round value if it is midway between two other numbers.

Returns

The number nearest to value that has a number of fractional digits equal to digits. If value has fewer fractional digits than digits, value is returned unchanged.

Exceptions

Remarks

Note

For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

Notes to Callers

Because of the loss of precision that can result from representing decimal values as floating-point numbers or performing arithmetic operations on floating-point values, in some cases the Round(Double, Int32, MidpointRounding) method may not appear to round midpoint values as specified by the mode parameter. This is illustrated in the following example, where 2.135 is rounded to 2.13 instead of 2.14. This occurs because internally the method multiplies value by 10digits, and the multiplication operation in this case suffers from a loss of precision.

using System;

public class Example
{
   public static void Main()
   {
      double[] values = { 2.125, 2.135, 2.145, 3.125, 3.135, 3.145 };
      foreach (double value in values)
         Console.WriteLine("{0} --> {1}", value, 
                           Math.Round(value, 2, MidpointRounding.AwayFromZero));

   }
}
// The example displays the following output:
//       2.125 --> 2.13
//       2.135 --> 2.13
//       2.145 --> 2.15
//       3.125 --> 3.13
//       3.135 --> 3.14
//       3.145 --> 3.15
Module Example
   Public Sub Main()
      Dim values() As Double = { 2.125, 2.135, 2.145, 3.125, 3.135, 3.145 }
      For Each value As Double In values
         Console.WriteLine("{0} --> {1}", value, 
                           Math.Round(value, 2, MidpointRounding.AwayFromZero))
      Next
   End Sub
End Module
' The example displays the following output:
'       2.125 --> 2.13
'       2.135 --> 2.13
'       2.145 --> 2.15
'       3.125 --> 3.13
'       3.135 --> 3.14
'       3.145 --> 3.15
See Also

Round(Double, MidpointRounding) Round(Double, MidpointRounding) Round(Double, MidpointRounding) Round(Double, MidpointRounding)

Rounds a double-precision floating-point value to the nearest integer. A parameter specifies how to round the value if it is midway between two numbers.

public:
 static double Round(double value, MidpointRounding mode);
public static double Round (double value, MidpointRounding mode);
static member Round : double * MidpointRounding -> double
Public Shared Function Round (value As Double, mode As MidpointRounding) As Double
Parameters
value
Double Double Double Double

A double-precision floating-point number to be rounded.

mode
MidpointRounding MidpointRounding MidpointRounding MidpointRounding

Specification for how to round value if it is midway between two other numbers.

Returns

The integer nearest value. If value is halfway between two integers, one of which is even and the other odd, then mode determines which of the two is returned.

Exceptions

Remarks

Note

For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

Notes to Callers

Because of the loss of precision that can result from representing decimal values as floating-point numbers or performing arithmetic operations on floating-point values, in some cases the Round(Double, MidpointRounding) method may not appear to round midpoint values to the nearest even integer. In the following example, because the floating-point value .1 has no finite binary representation, the first call to the Round(Double) method with a value of 11.5 returns 11 instead of 12.

using System;

public class Example
{
   public static void Main()
   {
      double value = 11.1;
      for (int ctr = 0; ctr <= 5; ctr++)    
         value = RoundValueAndAdd(value);

      Console.WriteLine();

      value = 11.5;
      RoundValueAndAdd(value);
   }
   
   private static double RoundValueAndAdd(double value)
   {
      Console.WriteLine("{0} --> {1}", value, Math.Round(value, 
                        MidpointRounding.AwayFromZero));
      return value + .1;
   }
}
// The example displays the following output:
//       11.1 --> 11
//       11.2 --> 11
//       11.3 --> 11
//       11.4 --> 11
//       11.5 --> 11
//       11.6 --> 12
//       
//       11.5 --> 12
Module Example
   Public Sub Main()
      Dim value As Double = 11.1
      For ctr As Integer = 0 To 5    
         value = RoundValueAndAdd(value)
      Next
      Console.WriteLine()

      value = 11.5
      RoundValueAndAdd(value)
   End Sub
   
   Private Function RoundValueAndAdd(value As Double) As Double
      Console.WriteLine("{0} --> {1}", value, Math.Round(value, 
                        MidpointRounding.AwayFromZero))
      Return value + .1
   End Function   
End Module
' The example displays the following output:
'       11.1 --> 11
'       11.2 --> 11
'       11.3 --> 11
'       11.4 --> 11
'       11.5 --> 11
'       11.6 --> 12
'       
'       11.5 --> 12
See Also

Round(Double, Int32) Round(Double, Int32) Round(Double, Int32) Round(Double, Int32)

Rounds a double-precision floating-point value to a specified number of fractional digits.

public:
 static double Round(double value, int digits);
public static double Round (double value, int digits);
static member Round : double * int -> double
Public Shared Function Round (value As Double, digits As Integer) As Double
Parameters
value
Double Double Double Double

A double-precision floating-point number to be rounded.

digits
Int32 Int32 Int32 Int32

The number of fractional digits in the return value.

Returns

The number nearest to value that contains a number of fractional digits equal to digits.

Exceptions

Remarks

Note

For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

Notes to Callers

Because of the loss of precision that can result from representing decimal values as floating-point numbers or performing arithmetic operations on floating-point values, in some cases the Round(Double, Int32) method may not appear to round midpoint values to the nearest even value in the digits decimal position. This is illustrated in the following example, where 2.135 is rounded to 2.13 instead of 2.14. This occurs because internally the method multiplies value by 10digits, and the multiplication operation in this case suffers from a loss of precision.

using System;

public class Example
{
   public static void Main()
   {
      double[] values = { 2.125, 2.135, 2.145, 3.125, 3.135, 3.145 };
      foreach (double value in values)
         Console.WriteLine("{0} --> {1}", value, Math.Round(value, 2));

   }
}
// The example displays the following output:
//       2.125 --> 2.12
//       2.135 --> 2.13
//       2.145 --> 2.14
//       3.125 --> 3.12
//       3.135 --> 3.14
//       3.145 --> 3.14
Module Example
   Public Sub Main()
      Dim values() As Double = { 2.125, 2.135, 2.145, 3.125, 3.135, 3.145 }
      For Each value As Double In values
         Console.WriteLine("{0} --> {1}", value, Math.Round(value, 2))
      Next
   End Sub
End Module
' The example displays the following output:
'       2.125 --> 2.12
'       2.135 --> 2.13
'       2.145 --> 2.14
'       3.125 --> 3.12
'       3.135 --> 3.14
'       3.145 --> 3.14
See Also

Round(Double) Round(Double) Round(Double) Round(Double)

Rounds a double-precision floating-point value to the nearest integral value.

public:
 static double Round(double a);
public static double Round (double a);
static member Round : double -> double
Public Shared Function Round (a As Double) As Double
Parameters
a
Double Double Double Double

A double-precision floating-point number to be rounded.

Returns

The integer nearest a. If the fractional component of a is halfway between two integers, one of which is even and the other odd, then the even number is returned. Note that this method returns a Double instead of an integral type.

Remarks

Note

For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

Notes to Callers

Because of the loss of precision that can result from representing decimal values as floating-point numbers or performing arithmetic operations on floating-point values, in some cases the Round(Double) method may not appear to round midpoint values to the nearest even integer. In the following example, because the floating-point value .1 has no finite binary representation, the first call to the Round(Double) method with a value of 11.5 returns 11 instead of 12.

using System;

public class Example
{
   public static void Main()
   {
      double value = 11.1;
      for (int ctr = 0; ctr <= 5; ctr++)    
         value = RoundValueAndAdd(value);

      Console.WriteLine();

      value = 11.5;
      RoundValueAndAdd(value);
   }
   
   private static double RoundValueAndAdd(double value)
   {
      Console.WriteLine("{0} --> {1}", value, Math.Round(value));
      return value + .1;
   }
}
// The example displays the following output:
//       11.1 --> 11
//       11.2 --> 11
//       11.3 --> 11
//       11.4 --> 11
//       11.5 --> 11
//       11.6 --> 12
//       
//       11.5 --> 12
Module Example
   Public Sub Main()
      Dim value As Double = 11.1
      For ctr As Integer = 0 To 5    
         value = RoundValueAndAdd(value)
      Next
      Console.WriteLine()

      value = 11.5
      RoundValueAndAdd(value)
   End Sub
   
   Private Function RoundValueAndAdd(value As Double) As Double
      Console.WriteLine("{0} --> {1}", value, Math.Round(value))
      Return value + .1
   End Function   
End Module
' The example displays the following output:
'       11.1 --> 11
'       11.2 --> 11
'       11.3 --> 11
'       11.4 --> 11
'       11.5 --> 11
'       11.6 --> 12
'       
'       11.5 --> 12
See Also

Round(Decimal, Int32) Round(Decimal, Int32) Round(Decimal, Int32) Round(Decimal, Int32)

Rounds a decimal value to a specified number of fractional digits.

public:
 static System::Decimal Round(System::Decimal d, int decimals);
public static decimal Round (decimal d, int decimals);
static member Round : decimal * int -> decimal
Public Shared Function Round (d As Decimal, decimals As Integer) As Decimal
Parameters
d
Decimal Decimal Decimal Decimal

A decimal number to be rounded.

decimals
Int32 Int32 Int32 Int32

The number of decimal places in the return value.

Returns

The number nearest to d that contains a number of fractional digits equal to decimals.

Exceptions

Remarks

Note

For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

See Also

Round(Decimal) Round(Decimal) Round(Decimal) Round(Decimal)

Rounds a decimal value to the nearest integral value.

public:
 static System::Decimal Round(System::Decimal d);
public static decimal Round (decimal d);
static member Round : decimal -> decimal
Public Shared Function Round (d As Decimal) As Decimal
Parameters
d
Decimal Decimal Decimal Decimal

A decimal number to be rounded.

Returns

The integer nearest parameter d. If the fractional component of d is halfway between two integers, one of which is even and the other odd, the even number is returned. Note that this method returns a Decimal instead of an integral type.

Exceptions

Remarks

Note

For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

See Also

Round(Decimal, MidpointRounding) Round(Decimal, MidpointRounding) Round(Decimal, MidpointRounding) Round(Decimal, MidpointRounding)

Rounds a decimal value to the nearest integer. A parameter specifies how to round the value if it is midway between two numbers.

public:
 static System::Decimal Round(System::Decimal d, MidpointRounding mode);
public static decimal Round (decimal d, MidpointRounding mode);
static member Round : decimal * MidpointRounding -> decimal
Public Shared Function Round (d As Decimal, mode As MidpointRounding) As Decimal
Parameters
d
Decimal Decimal Decimal Decimal

A decimal number to be rounded.

mode
MidpointRounding MidpointRounding MidpointRounding MidpointRounding

Specification for how to round d if it is midway between two other numbers.

Returns

The integer nearest d. If d is halfway between two numbers, one of which is even and the other odd, then mode determines which of the two is returned.

Exceptions

Remarks

Note

For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

See Also

Applies to