Percentage Calculator
Percentages are everywhere — sale discounts, exam scores, tax, tips, interest, battery drain — yet they are surprisingly easy to get wrong, because "percent" questions come in three different shapes that need three different formulas. This free calculator handles all three: finding a percentage of a number, expressing one number as a percentage of another, and measuring percentage change between two values. Each result shows its answer instantly, with no sign-up and no page reloads.
Who it is for: shoppers, students, small-business owners, and anyone who has ever stared at a bill wondering what 15% actually is. Example: a jacket is reduced by 30% from 85. Mode 1 tells you 30% of 85 is 25.5 — so you pay 59.5. Mode 3 then answers the follow-up: if a price rises from 59.5 back to 85, that is a 42.9% increase, not 30% — percentage changes are not symmetrical, and this calculator shows why.
Mode 1 — What is X% of Y?
Mode 2 — X is what percent of Y?
Mode 3 — Percentage change from X to Y
How to Use the Percentage Calculator
- Find the mode that matches your question — the three modes above cover nearly every everyday percentage problem.
- Type your numbers; results update as you type, so you can experiment freely.
- For discounts, Mode 1 gives the amount taken off; subtract it from the original price to get what you pay. For scores, Mode 2 turns marks into a percentage. For growth or decline, Mode 3 handles increases and decreases and labels the direction for you.
Frequently Asked Questions
What is the formula for each mode?
Mode 1: (X ÷ 100) × Y. Mode 2: (X ÷ Y) × 100. Mode 3: ((Y − X) ÷ X) × 100, reported as an increase if positive and a decrease if negative.
Why is a 30% discount followed by a 30% rise not back to the start?
Because the base changes. A 30% discount is calculated on the higher original price, while the 30% rise is calculated on the lower sale price, so the rise adds back less than the discount removed. Mode 3 makes this visible with real numbers.
What is the difference between percent and percentage points?
If an interest rate rises from 4% to 5%, that is a rise of 1 percentage point, but a 25% relative increase. News reports often blur the two; Mode 3 calculates relative change, which is usually what you want for growth and decline.
Can I use negative numbers or values over 100%?
Yes. Percentages above 100 are meaningful — for example, 250 is 250% of 100 — and Mode 3 handles decreases below the starting value, down to a 100% decrease at zero.
Percentages quietly run a large part of daily life. Our guide Percentages in Daily Life: The Maths Nobody Taught You Properly walks through discounts, tax, grades, and interest with worked examples.