How to use the percentage calculator
Start by choosing the question you need to answer. The four modes show the formula, the values placed into it, and the result. That gives you a calculation to check before you use Copy result or Download result (.txt).
Steps for calculating a percentage
- Choose % of a number, Is what percent of, Percent change, or Increase / decrease by %.
- Enter the values shown for that mode, such as Percentage and Number.
- Click Calculate. The result and the Steps list appear below the inputs.
- Use Copy result or Download result (.txt) when you need the plain-text calculation.
What each percentage calculator mode calculates
% of a number divides Percentage by 100 and multiplies the result by Number. Percentage 15 and Number 200 give 30.
Is what percent of divides Part by Whole and multiplies by 100. Part 30 and Whole 200 give 15%.
Percent change subtracts Old value from New value, divides by Old value, and multiplies by 100. Old value 50 and New value 65 give a 30% increase.
Increase / decrease by % applies the selected Direction to Number. Number 80 with Increase by and Percentage 25 gives 100.
15% of 200 = 30
30 is 15% of 200
50 to 65 = 30% increase
80 increased by 25% = 100Percentage calculator input rules and errors
Each input accepts a whole number or a decimal with an optional leading minus sign, such as -12.5. A decimal needs digits on both sides of the period. Blank values, commas, plus signs, exponents, and other unsupported characters produce an error.
- Whole must be nonzero in Is what percent of.
- Old value must be nonzero in Percent change.
- Negative numbers are accepted. A negative Percentage reverses Direction, so Increase by -10% acts as a 10% decrease.
- Percent change labels a nonnegative result Increase and a negative result Decrease.
- Changing an input hides the previous result. Click Calculate again to produce a new one. Displayed numbers are rounded to eight decimal places.
The calculation and result text are built in your browser from the values you enter. Copy result uses the clipboard when it is available. If copying fails, the page tells you to select and copy the text manually. Download result (.txt) creates a plain-text file.
Where percentage calculations come up
For a 15% discount on a price of 200, use % of a number with Percentage 15 and Number 200. The result is 30, the discount amount.
To compare scores, enter Old value 50 and New value 65 in Percent change. The result is a 30% increase.
For a completion rate, enter Part 30 and Whole 200 in Is what percent of. The result is 15%.
Percentage calculator or another math calculator?
Use Math Calculators for another kind of calculation. The Fraction Calculator handles fraction and mixed-number arithmetic. The Algebra Calculator handles linear or quadratic equations and small systems. For expressions with powers, roots, logarithms, trigonometry, constants, and percentages, use the Scientific Calculator.
Frequently asked questions
How do I calculate X% of a number?
Choose % of a number, enter Percentage 15 and Number 200, then click Calculate. The calculator divides 15 by 100 and multiplies it by 200, giving 30.
How do I find what percent one number is of another?
Choose Is what percent of, enter Part 30 and Whole 200, then click Calculate. The calculator divides 30 by 200 and multiplies by 100, giving 15%.
How is percentage increase or decrease calculated?
Choose Percent change, enter Old value 50 and New value 65, then click Calculate. The result is positive for an increase and negative for a decrease. Old value must be nonzero.
Why is percent change from 0 undefined?
Percent change divides by Old value. When Old value is 0, that division is undefined and the calculator shows an error.
How does Increase / decrease by % work?
Choose Increase / decrease by %, enter Number and Percentage, and select Increase by or Decrease by in Direction. A negative Percentage reverses the selected Direction.