Percentage calculator
This percentage calculator handles the three most common cases: what is X% of a number, how much did a value change in percent, and what percent one number is of another. Results update instantly as you type. Everything runs locally in your browser — no account, no install, and your numbers never leave your device.
Calculation mode
Percent (%)
Of number
Result
30
How to use the percentage calculator
1. Choose a mode: percent of a number, percent change, or what percent.
2. Enter the values (you can use a comma or a dot as the decimal separator).
3. Read the result — it recalculates automatically after each change.
4. Copy the result manually or try another example by switching modes.
Calculation examples
Percent of a number
You want to know what 23% of 890 is. In “percent of a number” mode, enter 23 and 890. Result: 204.70. Handy for tax, fees, and commission estimates.
Percent change
A price rose from 40 to 52. In percent-change mode, enter 40, then 52. Result: +30%. If it fell from 52 to 40, the result will be negative.
Share as a percent
45 out of 200 people voted. In “what percent” mode, enter 45 and 200. Result: 22.5%. Ideal for turnout, budget share, or project progress.
When to use this tool
• When you calculate discounts, VAT, commissions, or margins.
• When you compare price, salary, or traffic growth or decline.
• When you need a quick answer without opening a spreadsheet.
When to choose something else
• When you need compound interest over many periods — use a financial calculator.
• When you work in complex Excel or Google Sheets models with many variables.
• When the result must be part of official accounting — use proper bookkeeping software.
The formula and the intuition
A percent is simply a hundredth of a whole. When you say “15%”, you mean 15/100 = 0.15. So “15% of 200” is 200 × 0.15 = 30. The same rule applies to tax, discounts, and fees. Percent change works differently: it compares the difference to the starting value. If something goes from 100 to 120, the increase is 20% because the difference of 20 is 20% of 100. If you divided by 120 instead, you would get a different answer — which is why the reference point matters.
Common mistakes
The most frequent error is mixing up “percent of a number” with “percent change”. Another is dividing by zero or by the ending value instead of the starting one. A third is rounding too early in a chain of calculations. This calculator lets you pick the mode on purpose, which reduces mistakes. If you stack discounts one after another, remember that 10% + 10% is not always 20% off the original price, because the second discount applies to an already reduced amount.
Practical uses
Parents check store discounts and membership fees. Students verify math homework. Freelancers estimate VAT and platform commissions. Marketers compare CTR or conversion growth. In each case, a local browser calculator is faster than opening a spreadsheet — and it does not leave a history of your numbers on someone else’s server.
Frequently asked questions
How do I calculate a percent of a number?
Multiply the number by the percent and divide by 100. Example: 20% of 150 is 150 × 20 ÷ 100 = 30.
How do I calculate percent change?
Subtract the starting value from the ending value, divide by the starting value, and multiply by 100. A positive result means growth; a negative one means decline.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. Example: 25 of 200 is (25 ÷ 200) × 100 = 12.5%.
What is the difference between “percent of a number” and “percent change”?
“Percent of a number” answers “how much is X% of Y”. Percent change tells you how much a value rose or fell relative to where it started.
Can I enter fractions and decimals?
Yes. We accept both a dot and a comma as the decimal separator, e.g. 12.5 or 12,5.
Is my data sent to a server?
No. The calculator runs entirely in your browser — values are not stored or uploaded.
Is this tool free?
Yes. Use it without an account and without a limit on calculations.
Are results rounded?
Non-whole results are shown to two decimal places, which is enough for most everyday use.