Percentage calculator
Find a percent of a number, what percent one number is of another, the change between two values, or a discount.
Short answer
A percent is a fraction of 100. “20% of 150” is 150 × 0.20. Change is (new − old) ÷ old. A discount subtracts that fraction from the price.
How this works
Of: result = whole × percent ÷ 100. Ratio: percent = part ÷ whole × 100. Change: (ending − starting) ÷ starting × 100. Discount: savings = price × percent ÷ 100, and the new price is price minus savings.
A change from 80 to 100 is +25%, not +20 points. Points and percent are different, and this tool reports percent.
Examples
20% of 150
30.
From 80 to 100
A 25% increase.
Common mistakes
- Dividing the change by the new number instead of the starting number.
- Taking a discount off an already discounted price and adding the percents together.
Frequently asked questions
- Can the starting value be zero?
- Not for percent change. Dividing by zero is undefined, so the calculator asks you to change that input.
Related
- How to calculate a percentageTurn “percent of” into a multiplication by moving the decimal, and keep the whole amount in view.
- How to calculate percent changeCompare two numbers as a percent of the starting value, and do not divide by the ending value.
- How to take a percent off a priceSubtract a percent of the price from the price, and do not add stacked discounts into one percent.
- How to round moneyRound a currency result to the cent at the end, and avoid rounding the inputs first.