-= Operator (Visual Basic)

Subtracts the value of an expression from the value of a variable or property and assigns the result to the variable or property.

variableorproperty -= expression


  • variableorproperty
    Required. Any numeric variable or property.

  • expression
    Required. Any numeric expression.


The element on the left side of the -= operator can be a simple scalar variable, a property, or an element of an array. The variable or property cannot be ReadOnly (Visual Basic).

The -= operator first subtracts the value of the expression (on the right-hand side of the operator) from the value of the variable or property (on the left-hand side of the operator). The operator then assigns the result of that operation to the variable or property.


The - Operator (Visual Basic) can be overloaded, which means that a class or structure can redefine its behavior when an operand has the type of that class or structure. Overloading the - operator affects the behavior of the -= operator. If your code uses -= on a class or structure that overloads -, be sure you understand its redefined behavior. For more information, see Operator Procedures (Visual Basic).


The following example uses the -= operator to subtract one Integer variable from another and assign the result to the latter variable.

Dim var1 As Integer = 10
Dim var2 As Integer = 3
var1 -= var2
' The value of var1 is now 7.

See Also


- Operator (Visual Basic)

Assignment Operators (Visual Basic)

Arithmetic Operators (Visual Basic)

Operator Precedence in Visual Basic

Operators Listed by Functionality (Visual Basic)

Other Resources

Statements in Visual Basic