Percentage Calculator
Percentages describe a share out of 100, and the same handful of questions come up again and again: what is X% of Y, what percent does X make of Y, how much did a number change by, and what does a number become after a percent rise or fall. Pick the question, enter your two numbers, and get the answer with the working shown underneath.
How to use the percentage calculator
- Choose the type of percentage question from the drop-down — the labels on X and Y change to match.
- Enter the two values.
- Read the highlighted result, then check the steps below it to see exactly how it was worked out.
Formula
- X% of Y = X ÷ 100 × Y
- X as a % of Y = X ÷ Y × 100
- % change from X to Y = (Y − X) ÷ |X| × 100
- Increase Y by X% = Y × (1 + X ÷ 100)
- Decrease Y by X% = Y × (1 − X ÷ 100)
Worked examples
A discount
A ₹2,000 jacket is 15% off. 15% of 2,000 is 300, so the sale price is 2,000 − 300 = ₹1,700. "Decrease Y by X%" gives you ₹1,700 in one step.
A test score
You scored 30 out of 120. 30 ÷ 120 = 0.25, so that is 25%. Use "X is what % of Y" with X = 30, Y = 120.
Sales growth
Monthly sales rose from 50 to 65 units. (65 − 50) ÷ 50 × 100 = +30%. Use "% change from X to Y".
Where percentages show up in everyday life
The same five calculations on this page cover almost every percentage question that comes up day to day:
- Shopping discounts: "Decrease Y by X%" — a 30% off tag on a ₹2,000 item.
- Restaurant tips: "Increase Y by X%" — an 18% GST addition or a 10% service tip on a bill.
- Exam and test scores: "X is what % of Y" — converting a raw score like 42/50 into a percentage.
- Salary hikes and inflation: "% change from X to Y" — comparing last year's number to this year's.
- Interest and returns: "X% of Y" — quickly estimating simple interest or a one-off return before reaching for a full calculator.
A useful mental-math shortcut: 10% of any number is just moving the decimal point one place left (10% of 250 = 25), and you can build most other percentages from there — 5% is half of 10%, 20% is double 10%, 15% is 10% + 5%.
Common mistakes to avoid
- Percent change is measured against the starting value, not the ending one — a rise from 50 to 65 is +30%, but a fall back from 65 to 50 is only −23.08%.
- A 20% increase followed by a 20% decrease does not cancel out: 100 → 120 → 96.
- Percentage points and percent are different things — going from a 10% rate to a 12% rate is +2 percentage points, but a 20% relative increase.
Frequently asked questions
How do I find a percentage of a number?
Divide the percentage by 100 and multiply by the number — 15% of 80 is 0.15 × 80 = 12.
How do I calculate percent change?
Subtract the old value from the new one, divide by the old value, then multiply by 100. A positive answer is an increase; negative is a decrease.
Can a percentage be over 100?
Yes — 150% of 40 is 60. Anything above 100% simply means more than the whole original amount.
How do I undo a percentage increase?
Divide the new value by (1 + rate). If a price is 230 after a 15% rise, the original was 230 ÷ 1.15 = 200.
Reviewed September 29, 2026 by the CalcSolver editorial team. Found a mistake? Tell us; see our editorial policy.