Work out what X% of Y is, what % one number is of another, and increases or decreases — as you type.
What this percentage calculator does
Four everyday calculations in one box: what is X% of Y (a discount or share), X is what % of Y (a score or ratio), and increase / decrease Y by X% (markups, tax, reductions). All computed in the page.
Frequently asked questions
How is “X is what % of Y” worked out?
It divides X by Y and multiplies by 100. If Y is zero it shows a dash, because you cannot express a part of nothing.
Is anything uploaded?
No. The maths runs in your browser as you type.
Does it handle decimals?
Yes — enter values like 7.5 or 12.25; the result keeps full precision and is shown as typed.
How to use it
- Select a mode by clicking one of the four options at the top — of, is, inc, or dec — to set which kind of percentage you need.
- Type a value into X and a value into Y. The answer updates instantly as you type each digit.
- Switch modes without re-entering by clicking a different option; the numbers already in the fields remain unchanged and the formula recalculates.
- Copy the result by selecting the output text if you need to paste it into a note, spreadsheet, or email.
Where it comes in handy
A jacket costs £85 and is reduced by 30%. Select dec, enter 30 for X and 85 for Y, and the calculator returns £59.50 — the new price after the discount.
You got 14 correct answers out of 18 on a test. Choose the is option, type 14 and 18, and the result shows 77.78%.
A client invoice totals £2,400 before a 15% commission fee. Pick inc, put 15 in X and 2,400 in Y, and the adjusted amount is £2,760.
Worth knowing
- No automatic rounding. Results display full decimal precision. If you need two decimal places for a receipt, round the displayed number yourself rather than assuming the tool truncates.
- Division by zero returns a dash. The is mode shows a dash when Y is 0, because the calculation cannot produce a meaningful percentage from a zero denominator.
- Decimals are exact, not rounded mid-calculation. Entering 33.33 treats it as the literal value 33.33, not as an approximation of one-third. The final result is computed from the exact numbers you entered.