One percentage calculator for every real situation: find X% of a number (tax, tips), what percent X is of Y (marks, shares), percentage change between two values (growth, price rises), and increase-or-decrease by a percent (discounts, raises). Answers update live as you type, with the working shown so you can trust the number.
How to use it
- Pick the mode that matches your question's phrasing.
- Enter the two numbers — the answer appears instantly with the calculation spelled out.
- Switch modes freely; your numbers stay put.
Frequently asked questions
How do I calculate a percentage discount?
Use “Increase / decrease”: enter the price and the discount percent — the decreased value is your sale price. A 20% discount on 1,500 shows 1,200 instantly.
How do I find what percent one number is of another?
Use “X is what % of Y”: scoring 42 out of 60 → 42 is 70% of 60.
How is percentage change calculated?
(New − Old) ÷ Old × 100. Going from 80 to 100 is a +25% change; going from 100 to 80 is −20% — direction matters, which trips everyone up.
Why do I get a different answer reversing a percentage?
Because the base changes: +25% then −25% does not return you to the start. Always compute against the correct original value.
Related tools: the unit converter, days between dates and BMI calculator — all in our free daily tools.
The four percentage questions
Almost every real problem is one of these, and mixing them up is where mistakes come from:
- What is X% of Y? — 18% of 240. Multiply: 240 × 0.18 = 43.2
- X is what % of Y? — 43.2 out of 240. Divide: 43.2 ÷ 240 = 18%
- Percentage change — from 240 to 280. Difference ÷ original: 40 ÷ 240 = 16.7% increase
- Increase or decrease by X% — 240 plus 18% = 283.2
Why a 50% drop needs a 100% rise to recover
This one costs people real money. Percentage change is always measured against the starting figure, and the starting figure moves.
£100 falls 50% to £50. To get back to £100, that £50 must double — a 100% rise. The percentages are not symmetrical because they are calculated from different bases.
The same trap appears in discounts: 20% off then a further 10% off is not 30% off. It is 0.8 × 0.9 = 0.72, so 28%.
Percentage points are not percentages
If a rate rises from 4% to 6%, that is a 2 percentage point increase — and a 50% increase. Both are correct and they describe the same change.
Which one gets quoted usually depends on who is doing the quoting. A 50% rise sounds dramatic; 2 points sounds modest. When you read a statistic, check which is meant. When you write one, say which you are using.
VAT, tips and working backwards
Adding 20% VAT to £100 gives £120. Removing VAT from £120 is not subtracting 20% — that gives £96. You divide by 1.2, which gives £100.
The rule: to reverse a percentage increase, divide by (1 + rate), never subtract. This is the single most common percentage error in invoicing.
Calculated on your device
Nothing you type is sent anywhere. For unit work see the unit converter, and for date arithmetic the days between dates tool.