Calculators
Percentage Calculator
X% of Y, what percent, percentage change: the three calculations you need all the time.
X% of Y
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X is what % of Y?
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Change from X to Y
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A discount to apply, a margin to verify, a revenue trend to announce as a percentage: percentage maths comes up constantly, and a formula mix-up costs real money. This page gathers the three classic cases in three independent cards: how much is X% of Y (the discount, the commission, the tax); what percentage X is of Y (the share, the progress towards a target); and the percentage change between two values, plus or minus sign included (a price, an audience, a budget moving over time). Each result updates live, rounded to two decimals and formatted for your language. Free, no sign-up, and no formula traps to fall into.
How does it work?
- Pick the card that matches your question.
- Enter your two values — the result updates live.
- Read the result rounded to two decimals, sign included for changes.
Frequently asked questions
How do you calculate a percentage change?
The formula: (new value − old value) ÷ old value × 100. Revenue going from 80,000 to 92,000 francs grew by (92,000 − 80,000) ÷ 80,000 × 100 = +15%. Mind the classic trap: the starting value is always the reference — dropping from 100 to 80 is −20%, but climbing back from 80 to 100 is +25%.
How do I work out X% of an amount in my head?
Break it down: 10% means shifting the decimal point (10% of 340 = 34), 5% is half of that, 1% shifts it twice. So 18% of 340 = 34 + 34 − 6.8 = 61.2 — easy to fumble, hence this calculator. A handy trick: X% of Y equals Y% of X (8% of 25 = 25% of 8 = 2).
What is the difference between percentage points and percent?
A rate moving from 10% to 12% gains 2 percentage points but grows by 20% in relative terms (2 ÷ 10). Both statements are correct and mean different things — confusing them is one of the most common errors in business presentations and news reporting.
How do I find the original price before an X% discount?
You do not add the percentage back — you divide. An item bought for 170 francs after a 15% discount originally cost 170 ÷ 0.85 = 200 francs, not 170 × 1.15 = 195.50. The rule: after an X% decrease, divide by (1 − X/100); after an increase, divide by (1 + X/100).