X is what percent of Y?
If you scored 30 out of 150, what percentage did you get? Defaults to 30 of 150 = 20%.
This is the second of the three percentage directions: turning a part & whole into a percentage. Below: worked UK examples, the formula, and how to use it for marks, market share, and savings rates.
How it works. Standard part-over-whole formula. Multiply by 100 to express as a percentage.
Worked examples
£500 is 1.43% of £35,000 — what an extra £500 raise represents on a £35,000 salary (gross).
30 of 150 = 20% — e.g. a test where you got 30 out of 150 marks.
£250 is 0.83% of £30,000 — a typical car insurance excess as a percentage of a car's value.
£12,570 is 25.14% of £50,000 — the UK personal allowance as a share of a £50,000 salary.
£325,000 is 54.17% of £600,000 — the IHT nil-rate band as a fraction of a typical UK estate.
Sources:
HMRC personal allowance and tax bands
· retrieved 2026-05-12.
Frequently asked questions
What is the formula?
(X ÷ Y) × 100. The part divided by the whole, multiplied by 100.
Is this the same as a percentage increase?
No. This calculator tells you what fraction one number is of another. Percentage increase compares two values to find how much one has grown over the other — use the increase calculator for that.
How do I work out a percentage of a percentage?
If 20% is itself 30% of something, the answer is 30% of 20%, which is 6%. Multiply the two as decimals: 0.3 × 0.2 = 0.06 = 6%.
What if Y is zero?
The calculation is undefined — you can't divide by zero. The calculator returns no result in that case.