Percentage Calculator
Every percentage question in one place.
Percentage Calculator answers the six questions people actually ask: what is X% of Y, X is what percent of Y, percentage increase and decrease, percentage difference, and reverse percentage — the original number before a discount or a tax. Each mode shows the formula it used, and the arithmetic runs in your browser.
Loading Percentage Calculator…
Runs entirely on your device. No file or text you enter here is uploaded. How to verify it.
How to use Percentage Calculator
- Pick the mode that matches your question.
- Type the two numbers.
- Read the answer and the formula used to get it.
Questions about Percentage Calculator
What is the difference between percentage change and percentage difference?
Percentage change has a direction: it measures from an old value to a new one, so 50 to 75 is a 50% increase while 75 to 50 is a 33.3% decrease. Percentage difference is symmetric — it divides by the average of the two, giving 40% either way.
How do I find the price before VAT or a discount?
Use reverse percentage. If something costs 120 after a 20% markup, the original is 120 / 1.20 = 100 — not 120 minus 20%, which is the classic mistake and gives 96.
Why does a 50% drop need a 100% rise to recover?
Because the percentages are taken from different bases. Falling from 100 to 50 is 50 out of 100. Climbing from 50 back to 100 is 50 out of 50. Compounding percentages is not additive.
Does it work offline, and on a phone?
Yes. The page is a small script with no server round trip, so once it has loaded it keeps working with the connection off. Add it to your home screen from the browser menu and it opens like an app on iOS and Android.
Is there a limit on how large the numbers can be?
The arithmetic uses standard JavaScript double-precision numbers, which are exact for whole numbers up to about nine quadrillion. Beyond that, and for decimals such as 0.1 + 0.2, tiny rounding differences appear in the far digits. Results are rounded for display, so this only surfaces at extremes.
Is Percentage Calculator really free, with no limits?
Yes. There is no account, no daily cap, no file-size tier and no watermark, because there is no server cost to recover. The site is funded by clearly disclosed partner recommendations on the Partners page, never by metering the tools.
Are my files or text uploaded when I use Percentage Calculator?
No. Everything is processed by JavaScript running in your browser, on your device. You can verify it: open your browser's developer tools, switch to the Network tab, and use the tool. You will see no request carrying your data — because there is nowhere for it to go.