Percentage Calculator

The percentage calculator solves four everyday tasks: it finds a percent of a number, works out what percent one number is of another, and adds or subtracts a percentage. Pick a mode, enter two numbers – the result appears instantly, together with the formula. All calculations happen on your device.

How to use the calculator

Choose a mode with the buttons at the top. "Percent of a number" is the classic task: how much is 15% of a paycheck or 20% of a price. "What percent is" solves the reverse problem: what share one number is of another – for example, what percent of the exam questions were answered correctly. "Add percent" and "Subtract percent" come in handy for prices and metrics: a tax added to a price, weight down by a few percent, interest credited to a deposit. Percentages can be entered with decimals: 2.5, 0.5, 12.75.

Percent formulas

Percent of a number: result = number × percent ÷ 100. Example: 15% of 3000 = 3000 × 15 ÷ 100 = 450. What percent one number is of another: result = part ÷ whole × 100. Example: 450 of 3000 = 450 ÷ 3000 × 100 = 15%. Adding and subtracting a percent: result = number ± number × percent ÷ 100. Example: 3000 + 15% = 3450, and 3000 − 15% = 2550.

Reverse percentage: why +20% and −20% do not cancel out

A classic trap: a price is raised by 20%, then cut by 20% – and people expect the original price back. In fact the result is lower: 100 → +20% → 120 → −20% → 96. That is because the second percent is taken from the already increased number. To bring a price of 120 back to 100, you cut not 20% but 16.67% – this is the "reverse percentage". You get it by dividing: 100 ÷ 120 × 100 ≈ 83.33%, that is, a cut of 16.67%.

Where you meet percentages every day

Discounts in stores and sales, taxes and deductions from a paycheck, tips at a café, interest on deposits and loans, figures in reports and statistics, ingredient ratios in recipes. Being able to take a percent of a number in your head saves time: 10% is a tenth, 5% is half of that, 50% is half the number. For everything else, a calculator is easier.

This calculator is for information only. When calculating taxes and financial obligations, check the rules of your country.

Frequently asked questions

How do I calculate a percent of a number?
Multiply the number by the percent and divide by 100. Example: 15% of 2000 = 2000 × 15 ÷ 100 = 300. In the calculator, pick "Percent of a number", enter the number and the percent – the result appears instantly.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. Example: 30 of 150 = 30 ÷ 150 × 100 = 20%. In the calculator this is the "What percent is" mode: the first field is the part, the second is the whole.
How do I add a percent to a number?
Add the number to its percentage share: result = number + number × percent ÷ 100. Example: 500 + 10% = 500 + 50 = 550. The "Add percent" mode does this in one step.
Why do +20% and −20% not return the original number?
Because the second percent is taken from the already changed number: 100 → +20% → 120 → −20% → 96. To bring 120 back to 100 you must subtract not 20% but 16.67% (reverse percentage: 100 ÷ 120 × 100 ≈ 83.33%).
How do I calculate a percent of a percent?
Step by step: first take the percent of the number, then the percent of the result. Example: 10% of 50% of 200 – first 50% of 200 = 100, then 10% of 100 = 10. Two "of"s in a row mean multiplying the shares: 0.10 × 0.50 × 200 = 10.
How do I work out percentages quickly in my head?
Anchor points: 10% is dividing by 10, 5% is half of 10%, 50% is half the number, 25% is a quarter. Example: 15% of 240 = 10% (24) + 5% (12) = 36. For trickier numbers, take 1% (a hundredth) and multiply it by the percent you need.

Updated: Oct 15, 2026

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