Percentage Calculator
Calculate percentages in multiple ways
Formulas
About the Percentage Calculator
This percentage calculator covers all the directions people actually need: what percent of a number, the percentage change between two values, adding or removing a percentage, and working backwards from a total to find the original figure.
A percentage calculator saves the step everyone gets wrong under pressure — which number goes on the bottom. Each mode here is labelled by the question it answers, so there is no need to remember whether to divide by the old value or the new one.
The reverse mode is the one worth knowing about. If a price is £120 after 20% VAT, the original is not £96 — dividing by 1.2 gives £100. The same trap catches discounts: a 25% reduction to £75 came from £100, not £93.75. Working backwards is a division, not a subtraction.
Percentage change between two values is also handled explicitly, including the asymmetry that surprises people: going from 50 to 100 is a 100% increase, but going from 100 back to 50 is only a 50% decrease.
How to use the Percentage Calculator
- Choose the calculation. Pick percent of a number, change between values, increase, decrease or reverse.
- Enter your numbers. Fill in the two values the selected mode asks for.
- Read the answer. The result updates as you type, with the working shown.
- Switch modes to check. Use the reverse mode to confirm a figure you calculated forwards.
Percentage Calculator features
- What is X% of Y
- X is what percent of Y
- Percentage change between two values
- Working backwards: X is P% of what
- Recalculates as you type
- Runs in your browser; nothing is uploaded
Frequently asked questions
Which calculation do I need?
Use X% of Y for a discount or a tip. Use X is what % of Y for a share of a total. Use % change when comparing before and after. Use X is P% of what to recover an original figure from a part — the one people get wrong most often.
How do I find the original price before a discount?
Use the reverse mode. A sale price of £80 after 20% off is 80% of the original, so the original is 80 ÷ 0.8 = £100. Subtracting 20% from £80 gives £64, which is the mistake this mode exists to prevent.
Why is a 50% fall not undone by a 50% rise?
Because each percentage applies to a different base. 100 falling 50% gives 50, and 50 rising 50% gives 75. Percentage changes do not cancel out, which is why investment returns are so easy to misread.
What is the difference between percentage points and percent?
A rate moving from 4% to 5% has risen by one percentage point, but by 25 percent. Both statements are true and they describe very different things, so the distinction matters whenever rates are being compared.
Are my figures sent anywhere?
No. Everything is computed in your browser, so the numbers you enter are never transmitted or stored.