Napkin Math in OneNote

In addition to being a great place to store all of your notes and other content, OneNote also serves as a calculator. For example, say you're taking some notes and you suddenly have to do some quick arithmetic. You can either try to uncover those dusty memories of how to do fundamental mathematics in the far-reaching, (and in my case, dark), corners of your brain…or, just let OneNote's Napkin Math feature figure out the result for you.

Here's how it works. Just type the equation anywhere on OneNote's page surface, followed by an equals sign "=" and as soon as you press the <Spacebar> or <Enter>, OneNote performs the calculation.  For example, let's say you want to calculate the average monthly sales of bolts that sell 70 thousand per year: just type "70,000 / 12 = ". Once you press the <Spacebar> OneNote does the following: "70,000 / 12 = 5,833.3333".

Or perhaps your in a meeting discussing the purchase of 18 new company vehicles for your sales force at $29,000 a car.  Just enter "18 * $29,000 = ". OneNote resolves to "18 * $29,000 = $522,000.00". Notice the automatic inclusion of the decimal point (.) in the result. That's because of the dollar sign ($).

If you want to figure out the monthly payment of a loan you're about to take out just use pmt(i; n; b) , where i = interest rate, n = number of payments and b = the amount borrowed. So if you type the following equation: "pmt(.019; 36; $50,000) = " you'll get: "pmt(.019; 36; $50,000) = $1,930.28".

Maybe you just want to impress your fellow classmates by showing them how quickly you can work out the answers to those complicated calculations.  Tip: Just don't let them see your fingers typing away on the keyboard.

Whatever the reason, you're sure to benefit from OneNote's built-in calculator.

Here are some more examples of expressions that can be calculated in OneNote:

  • You type: "sin(30) = ". OneNote resolves to: "sin(30) = 0.5"
  • You type: "(6 + 7) / (4 * sqrt(3)) = ". OneNote resolves to: "(6 + 7) / (4 * sqrt(3)) =1.876388374866284"
  • You type: "5 ^ 4 = ". OneNote resolves to: "5 ^ 4 = 625"

See below for a list of supported operators and math/trig functions.


  • Use the percent sign (%) to make calculating percentages easier
    • Type: "35 * 20 % = ", you get: "35 * 20 % = 7"
  • Lower case x, upper case X and asterisk (*) are all valid multiplication operators
    • "2 x 3 X 5 *9 = " resolves to: "2 x 3 X 5 *9 = 270"
  • You can use pi and phi as constants
    • "1 * pi= " resolves to: "1 * pi = 3.141592653589793"
    • "1 * phi= " resolves to: "1 * phi = 1.618033988749895"
  • Factorial numbers are computed like so:
    • "5 ! = " resolves to: "5 ! = 120"
  • Use 'mod' to calculate remainders
    • "38 mod 12 = " resolves to: "38 mod 12 = 2"
  • To disable napkin math in OneNote, click Tools -> Options -> remove the checkmark from Calculate mathematical expressions automatically.
  • Be sure the symbols you use in your equation are valid symbols. For example, try typing " #38 mod 12 = ". You would probably expect a result of 2. However, because the hash mark "#" invalidates the number 38, OneNote is really solving the equation "12 =", for which the result is 12.
  • Finally, here's a note from John Guin's blog on napkin math:

And here is the final part that surprised me the most. The Greek letters for pi and phi are supported as constants in both lower case and capital forms. Try it out:

π= should give 3.141592653589793

Π=should give 3.141592653589793

φ=should give 1.618033988749895

Φ=should give 1.618033988749895

(Use character map to insert the symbols if you want).

List of supported operators:

Arithmetic operator Meaning Example
+ (plus sign) Addition 3+3
– (minus sign) Subtraction, Negation 3–1, –1
* (asterisk) Multiplication 3*3
X or x Multiplication 3x3
/ (forward slash) Division 3/3
% (percent sign) Percent 20%
^ (caret) Exponentiation 3^2
! (exclamation) Factorial computation 5!

List of math and trigonometry functions:

Function Description Syntax
ABS Returns the absolute value of a number ABS(number)
ACOS Returns the arccosine of a number ACOS(number)
ASIN Returns the arcsine of a number ASIN(number)
ATAN Returns the arctangent of a number ATAN (number)
COS Returns the cosine of a number COS(number)
DEG Converts an angle (in radians) to degrees DEG(angle)
LN Returns the natural logarithm of a number LN(number)
LOG Returns the natural logarithm of a number LOG(number)
LOG2 Returns the base-2 logarithm of a number LOG2(number)
LOG10 Returns the base-10 logarithm of a number LOG10(number)
MOD Returns remainder of a division operation (number)MOD(number)
PI Returns the value of π as a onstant PI
PHI Returns the value of φ (the golden ratio) PHI
PMT Calculates a loan payment based on a constant interest rate, a constant number of payments, and the present value of the total amount PMT(rate;nper;pv)
RAD Converts an angle (in degrees) to radians RAD(angle)
SIN Returns the sine of the given angle SIN(angle)
SQRT Returns a positive square root SQRT(number)
TAN Returns the tangent of a number TAN(number)