How to calculate a percentage of a number
Multiply the number by the percentage and divide by 100: Y × X ÷ 100. For example, 15% of 2,500 is 2,500 × 15 ÷ 100 = 375, and 0.25% of 2,000 is 5. This percentage calculator, or percent calculator, shows the result as you type.
How to find what percent of a number another number is
Divide the part by the whole and multiply by 100: (X ÷ Y) × 100. For example, 375 out of 2,500 is 375 ÷ 2,500 × 100 = 15%. This answers “what percent of a number is this?”. If the whole (Y) is 0, there is no answer, because it would mean dividing by zero.
How to calculate a percentage increase or decrease
Subtract the original from the new value, divide by the original and multiply by 100. Going from 1,000 to 1,200 is a 20% increase; from 1,200 to 900 is a 25% decrease. Use it as a percentage increase calculator or a percentage decrease calculator. A change from 0 has no defined percentage. If the original is negative, the change is measured against its size (absolute value) so the sign still shows the direction, and a note explains this.
How to reverse a percentage or discount
If you know the value after a change, divide by (1 − rate ÷ 100) for a decrease or (1 + rate ÷ 100) for an increase. After a 15% discount, a price of 850 was 850 ÷ 0.85 = 1,000 before; a price of 1,070 including 7% tax was 1,070 ÷ 1.07 = 1,000. A reverse percentage calculator does this for you. Adding 15% of 850 back gives 977.50, which is wrong.
Common mistakes in percentage calculations
A 20% cut followed by a 20% rise doesn't return to the start (100 → 80 → 96). Percentage points are not percentages: a rate going from 2% to 3% rises by 1 point, which is a 50% increase. Write decimals with a dot, such as 1.5; “1,5” could mean 1.5 or 15, so the calculator asks you to clarify.
Frequently asked questions
Can I type Thai digits?
Yes. ๒๕๐๐ and ๑๕.๕ work the same as 2500 and 15.5.
How are results rounded?
Calculations are exact and rounded once for display, to at most 6 decimals. For example, 1 out of 3 is about 33.333333%, and the result is labelled as rounded.
Are my numbers saved or sent anywhere?
No. Everything is calculated in your browser. Numbers leave the page only if you choose to share them.