What Percentage Is X of Y?

Part divided by whole

To find what percentage one number is of another, divide the part by the whole and multiply by 100.

part ÷ whole × 100 = percentage

The only thing to get right is which number is which. The whole is the total, the original, the thing being measured against. The part is the piece of it.

A quick check on your answer

If the part is smaller than the whole, the answer must be under 100 %. If it is larger, the answer is over 100 % — which is perfectly valid. Scoring 110 % on a test with bonus marks is a real thing, and so is a company making 250 % of its target.

Getting an answer on the wrong side of 100 almost always means the two numbers went in the wrong boxes.

Common uses

• Marks and scores — 34 out of 40 is 85 %.
• Completion and progress — how far through something you are.
• Share of a total — what proportion of a budget one line represents.
• Conversion rates, which are this calculation with different names on the boxes.

The working, step by step

Questions people ask

How do I find what percentage one number is of another?

Divide the part by the whole and multiply by 100. 12 out of 80 is 12 ÷ 80 × 100 = 15 %.

Can the answer be more than 100%?

Yes, whenever the part is bigger than the whole. That is normal for targets, growth and bonus marks.

Which number goes first?

The part — the smaller piece you are measuring. The whole is the total you are measuring against.

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