Percentage Calculator

The three percentage questions you actually ask — a percent of a number, one number as a percent of another, and the percent increase or decrease between two numbers.

Result —

How to Calculate Percentages

Pick the question that matches what you need.

1

Choose a mode

"% of a number" for a part of a whole, "X is what % of Y" for a ratio or score, or "% increase / decrease" for a before-and-after change.

2

Enter two values

The two input labels change to match the mode so you always know what each box means. Decimals and negatives are fine.

3

Read the answer

The result and a plain-English explanation update as you type. Working out a tip instead? The Tips Calculator adds and splits it for you.

Frequently Asked Questions

How do I find a percentage of a number?
To find X% of Y you multiply Y by X and divide by 100. For example, 15% of 80 is 80 × 15 ÷ 100, which is 12. The "percent of a number" mode does this for you: type the percentage in the first box and the number in the second, and the answer updates instantly. This is the calculation behind sales tax, a discount amount, a tip, or a commission — anywhere you need a part of a whole expressed as a percentage.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, if 18 students out of 24 passed, that is 18 ÷ 24 × 100, which is 75%. The "X is what percent of Y" mode handles this: enter the part first and the whole second. It is the right mode for a test score, a completion rate, or what share one amount is of a total. If the whole is zero the answer is undefined, and the calculator shows a note instead of a misleading number.
How is percent increase or decrease calculated?
Percent change is the difference between the new and old values divided by the old value, times 100. The formula is (new − old) ÷ old × 100. Going from 50 to 65 is (65 − 50) ÷ 50 × 100, a 30% increase; going from 80 to 60 is a 25% decrease, shown as a negative percentage. Use this mode for price changes, growth rates, or any before-and-after comparison. The old value cannot be zero, since you cannot express a change as a percentage of nothing.
Is the percentage calculator free and private?
Yes. It is completely free with no account or sign-up, and every calculation runs in your browser using plain arithmetic. The numbers you type are never uploaded or stored, so nothing is logged and the tool keeps working offline once the page has loaded. It handles negatives and decimals, and switching modes keeps your numbers in place so you can compare the same values three different ways.