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Percentage Calculator

Work out what X% of Y is, what percentage one number is of another, and percentage increase or decrease. Three calculators in one.

Runs on your device — nothing is uploaded

Three percentage questions, one tool: what is X% of Y, X is what percent of Y, and percentage increase or decrease.

How to use this tool

  1. Pick the question you are asking.
  2. Enter the two numbers.
  3. The answer appears with the working shown underneath.

The three calculations

What is X% of Y? Multiply and divide by 100. 15% of 200 = 200 × 15 ÷ 100 = 30. This is the one for discounts, tips, and tax.

X is what % of Y? Divide and multiply by 100. 30 out of 200 = 30 ÷ 200 × 100 = 15%. This is the one for scores, shares, and conversion rates.

Percentage increase or decrease The change divided by the original value. From 200 to 250 is a 25% increase, because 50 ÷ 200 = 0.25.

The mistake almost everyone makes

Percentage changes do not cancel out. A price rises 20% then falls 20% — you are not back where you started. £100 → £120 → £96. The increase and decrease are calculated on different bases.

Similarly, going from 5% to 10% is a 5 percentage point increase but a 100% increase. Reporting these interchangeably is how misleading statistics get made. When the quantity is itself a percentage, say "percentage points" and there is no ambiguity.

Worked examples

  • 20% off £45 → 20% of 45 = 9, so you pay £36
  • A 15% tip on a £68 bill → £10.20, total £78.20
  • Scored 43 out of 60 → 43 ÷ 60 × 100 = 71.7%
  • Rent went from £900 to £990 → 10% increase

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FAQ

Is anything uploaded?

No — it is arithmetic in your browser.

How do I remove a percentage that has already been added?

Divide, do not subtract. To strip 20% VAT from £120: 120 ÷ 1.2 = £100. Subtracting 20% of 120 would give £96, which is wrong.

What is the difference between percent and percentage points?

Percent is relative, percentage points are absolute. Interest going from 2% to 3% is a rise of 1 percentage point or 50 percent — both true, wildly different impressions.

Can percentage increase exceed 100%?

Yes. Doubling is a 100% increase; tripling is 200%. A decrease cannot exceed 100%, since that would mean going below zero.

Why does percentage change from zero not work?

Because you would divide by zero. Any increase from nothing is undefined as a percentage — report it as an absolute change instead.

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