Percentage Calculator
Three of the most common percentage questions, one small tool. Pick the one you need, type your numbers, and see the answer along with the working.
Explain like I'm 5 (what even is this calculator?)
It does three percentage sums for you. "What is 20% of 150?" gives you 30. "25 is what percent of 200?" gives you 12.5%. "What is the percentage change from 100 to 150?" gives you +50%. That is all. No sign-up, no catch.
Calculate
Enter values and press Calculate.
Prove it
Definition: a percentage is a fraction of 100. 15% means 15 per 100, or 0.15 as a decimal.
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The three kinds of percentage question
Almost every percentage sum falls into one of three shapes, and spotting which shape you are looking at is half the battle.
1. What is A% of B?
You have a percentage and a total; you want the part. A tip of 15% on a £62 bill, 20% off a £45 jumper, or 5% tax on an £800 laptop. The formula: (A ÷ 100) × B. 15% of 200 is (15 ÷ 100) × 200 = 30.
2. A is what % of B?
You have a part and a whole; you want the percentage. You scored 42 on a 60-mark paper and want to know the grade. 38 people replied to a survey of 150: what response rate is that? The formula: (A ÷ B) × 100. 50 out of 200 is (50 ÷ 200) × 100 = 25%.
3. Percentage change from A to B
You have a starting number and a new number; you want the move. A stock went from 80p to 100p, a house from £220,000 to £240,000, a weight from 90 kg to 83 kg. The formula: ((B − A) ÷ A) × 100. From 100 to 150 is ((150 − 100) ÷ 100) × 100 = +50%. From 200 to 100 is a −50% change, a halving.
Common pitfalls
A 50% loss is not undone by a 50% gain. Lose half of £100 and you have £50. Add 50% and you are at £75, not back to £100. It takes a 100% gain from £50 to return to £100. That asymmetry trips up a lot of headline-writing.
"Percentage points" and "percent" are not the same. If a poll rating moves from 40% to 44%, that is a rise of 4 percentage points, or a 10% increase. The two phrasings mean different things and get mixed up constantly.
Related calculators
Percentages show up everywhere. Here are the everyday sums that use them.
Frequently asked questions
What is 15% of 200?
15% of 200 is 30. The calculation is (15 ÷ 100) × 200 = 30.
How do I work out what percentage one number is of another?
Divide the part by the whole, then multiply by 100. For example, 50 out of 200 is (50 ÷ 200) × 100 = 25%.
How is percentage change calculated?
Subtract the starting value from the ending value, divide by the starting value, then multiply by 100. From 100 to 150, that is ((150 − 100) ÷ 100) × 100 = 50%.
Does this calculator send my numbers anywhere?
No. Everything runs in your browser. The numbers you type never leave your device.