Percentage calculator that shows the working
Everyday percentages and the mark you need in your exam. Free, no sign-up; calculated in your browser.
What is ___% of ___?
Type both numbers to see the answer.
Working:
Points are the plain gap. The % change compares that gap with where you started.
Decimal places
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What mark do I need in my exam?
For coursework, mocks and papers that count for different amounts.
Add each part with what it's worth. Leave the score empty for anything still to come.
Fix the highlighted boxes to see the result.
Some courses also need a minimum in each part; this page does not check that.
Decimal places
Clear every part and the target?
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How the percentage calculator works
Every sum here is one line of arithmetic, written out for you with your numbers in it. 15% of 80 is 15 ÷ 100 = 0.15, then 0.15 × 80 = 12. 23 out of 40 is 23 ÷ 40 × 100 = 57.5%. A rise or a fall becomes a multiplier: up 2.5% is × 1.025, down 20% is × 0.8. A reverse percentage divides by that same multiplier to get back to where you started.
An = sign means the answer is exact. ≈ means it's been rounded to the decimal places you picked, half up, the way you were taught at school. Behind the screen it's all exact fractions, not the binary decimals most web pages run on. That's why 29 out of 100 comes out at 29%, not 28.999999999999996%.
The exam panel treats each part's weight as a share of the total. Coursework worth 30 and an exam worth 70 add up to 100. Three papers worth 80 marks each add up to 240, and each one still counts for a third. From there the panel adds up what you've already secured, takes it off your target and spreads the rest across the parts still to come. What you need is always rounded up, so it's never a mark short. Your lowest and highest possible finishes are rounded down, so they never promise more than the marks can give.
Who this is for
You've got a number in front of you and you want the percentage, fast: a test back with 34 out of 50 on it, a pay rise to check, a coat that's 20% off. Or you're somewhere between Year 10 and Year 13 with a mock done, coursework marked and one paper left, and you want to know what it'll take. Parents on homework duty get the same working the pupil does, which may even settle the argument about method.
University students can use the exam panel for a module made of assignments and an exam. What it won't do is turn a percentage into a GCSE or A level grade. In England, those boundaries aren't set until after the exams.
Student and parent questions about percentages
How do you work out a percentage of an amount?
Divide the percentage by 100 and multiply by the amount. 15% of 80 is 0.15 × 80, which is 12. Without a calculator, find 10% first by dividing by 10, then build up: 10% of 80 is 8, 5% is 4, so 15% is 12. Both routes land on the same answer, and the working you get here follows the first.
How do I work out a percentage of my marks?
Divide your mark by the total and multiply by 100. 23 out of 40 is 23 ÷ 40 × 100 = 57.5%. To the nearest whole number that's 58%, because a 5 rounds up. Computers can trip on this one: in the binary arithmetic most web pages use, 23 ÷ 40 × 100 comes out a hair under 57.5, and rounding that gives 57. Ours works in exact fractions, so it says 58.
How do you work out percentage increase?
Take the old number from the new one, divide by the old one and multiply by 100. A mock that goes from 54% to 63% is (63 - 54) ÷ 54 × 100, about 16.67%. A fall uses the same sum and comes out negative: 80 down to 60 is -25%, a 25% decrease. Always divide by where you started.
What's the difference between percentage points and percentage change?
Percentage points are the plain gap between two percentages. Percentage change compares that gap with where you started. From 54% to 63% is 9 percentage points, and it's also a 16.67% rise. Both are true. They just answer different questions. Type the % signs in the change sum and you get both.
How do you work out reverse percentages?
Divide by the multiplier instead of multiplying. A coat costs £48 after 20% off, so £48 is 80% of the original: £48 ÷ 0.8 = £60. The classic slip is adding 20% of £48 back on, which gives £57.60. The 20% came off £60, not off £48.
How do I work out my overall percentage with different weightings?
Multiply each score by its weight, add them up and divide by the total weight. Coursework at 90% worth 20%, and an exam at 60% worth 80%, gives 0.2 × 90 + 0.8 × 60 = 66%. Averaging the two as if they counted the same gives 75%, nine points too high.
How do I work out the mark I need in my exam?
Work out what you've already banked, take it off your target and divide by what the exam is worth. Coursework at 72% worth 40% banks 28.8 points towards a 70% target. The exam's 60 has to bring the other 41.2, which is about 68.67% of it. On an 80-mark paper that's just under 55 marks, so you need 55. Settle for 54 and you finish on 69.3%.
What percentage is a grade 4 or a grade 7 at GCSE?
There isn't a fixed one. Ofqual, the exams regulator in England, is plain about it: "Grade boundaries change from year to year", and they're "decided after students take exams and when marking is nearly complete". They also "typically differ between exam boards". AQA, for one, publishes its boundaries at 8am on results day. Last year's boundary is a fair thing to aim at, never a promise. Type it in as your target, out of the total it was published with.
How to work out a percentage
Most percentage questions you'll meet come in one of three shapes. "What is 15% of 80?" wants part of an amount, so multiply by 0.15. "23 out of 40 as a percentage" wants a share, so divide and times by 100. "From 54 to 63" wants a change: subtract, divide by the start, times by 100.
Turn the percentage into a multiplier and the rest follows. Up 15% is × 1.15. Down 30% is × 0.7. A reverse percentage question wants the original back. Divide by the multiplier rather than adding the percentage back on: a jacket that's £35 after 30% off was £35 ÷ 0.7 = £50.
When a question says "give your answer to 1 decimal place", keep the full number until the end and round once. Round 3 ÷ 7 to 0.43 halfway through and you get 43.0% instead of 42.9%. Set the decimal places to match the question, and your answer gets the same treatment: one rounding, at the very end.
Sources and last checked
- Grade boundaries: Ofqual, "GCSE and A level grading: what you need to know" (updated 9 April 2025).
- When boundaries are published: AQA, "Grade boundaries" (exams administration pages).
- The arithmetic itself uses no data tables, so nothing else here goes out of date.
- Last checked: 7 October 2026.
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