What it does
The percentage calculator answers the three everyday percentage questions:
- Percent of: what is 15% of 200? (30)
- What percent: 30 is what percent of 200? (15%)
- Change: what is the percentage change from 80 to 100? (+25%, an increase of 20)
The answer updates as you type, and the sum under it uses your own numbers, so you can check how it was worked out.
How to use it
- Under Calculate, choose Percent of, What percent or Change.
- Type your two numbers. The result appears as soon as both are filled in.
- Select Copy result to put the answer on your clipboard, with the difference and direction for a change.
The calculator remembers the sum you chose and your numbers on this device, so they’re there the next time you open the page.
How it’s calculated
- Percent of: percent ÷ 100 × number. For example 15 ÷ 100 × 200 = 30.
- What percent: value ÷ total × 100. For example 30 ÷ 200 × 100 = 15%.
- Change: (To − From) ÷ |From| × 100. For example (100 − 80) ÷ |80| × 100 = +25%. The change is measured against the starting value, From. When From is negative, its size is used, so a rise always shows as an increase. The result also shows the plain difference, To − From, and whether it’s an increase, a decrease or no change.
Results are rounded for display only: at most 4 decimal places, with trailing zeros dropped. A result that isn’t 0 but is smaller than that keeps 6 significant digits instead, so 10% of 0.0001 shows as 0.00001 rather than 0.
Good to know
- Each number can be anything from −1,000,000,000,000,000 to 1,000,000,000,000,000, with any number of decimals. The calculator asks you to fix a number outside that range.
- What percent can’t divide by a Total of 0, and Change can’t start from a From of 0: there’s no answer, and the field says so. A number extremely close to 0, such as 1e-300, can make the answer too large to show, and that field is marked too.
- A change of +100% doubles the starting value, and −100% takes it to 0. Changes can be larger than 100%.
- For a discount or a tax, Percent of gives the amount to take off or add: a 20% discount on 50 is 20% of 50 = 10, so the price falls to 40.
Privacy
Everything is calculated in your browser, on your device. Nothing you type is uploaded. Only your chosen sum and numbers are kept, in this browser’s storage, so the page can show them again.