How do I calculate a percentage of a number?

Multiply the number by the percentage and divide by 100: 20% of 80 = 80 × 20 ÷ 100 = 16.

How do I express a value as a percentage of another?

Divide the part by the whole and multiply by 100: 30 out of 120 → 30 ÷ 120 × 100 = 25%.

What is the difference between a percentage point and a percent?

A percentage point is the absolute difference between two percentages; a percent change is the relative difference. Going from 10% to 12% is +2 percentage points, which is also a +20% change.

Can I work backwards to the original number?

Yes. If you know the result and the rate, divide the result by the rate: a price of 54 after a 10% discount started at 54 ÷ 0.9 = 60, and a value of 46 after a 15% increase started at 46 ÷ 1.15 = 40.

Can a percentage be higher than 100%?

Yes. Doubling is a 100% increase and tripling is a 200% increase. Only a part of a whole — a test score or a market share, for example — is capped at 100%.

Percentage Calculator

Work out a percentage of a number, or express one value as a percentage of another.

What is B% of A?

of% =

A is what % of B?

isof%

What Is a Percentage?

A percentage is a fraction whose denominator is always 100 — the word comes from the Latin per centum, meaning "by the hundred". So 25% is exactly 25/100, or 0.25. Because every percentage is measured against the same base of 100, it makes very different quantities directly comparable: a 30% discount, a 4.5% interest rate and a 20% test score all read on the same scale. Percentages behave like fractions in arithmetic — the only extra step is multiplying or dividing by 100 when converting to and from decimal form.

Percentage Formulas

B% of A = A × (B / 100)

A out of B = (A / B) × 100 (%)

Here A is the base amount and B is the rate in percent, so the answer is A scaled by B/100. To turn a part into a percentage, divide the part by the whole first and multiply by 100 second.

Worked Examples

What is 20% of 150? → 150 × (20 ÷ 100) = 30

30 is what percent of 150? → (30 ÷ 150) × 100 = 20%

A share price rises from 40 to 46 → (46 − 40) ÷ 40 × 100 = 15% increase

Percentage Points vs. Percent

A percentage point is the arithmetic difference between two percentages, while a percent change is the relative difference. Moving from 10% to 12% is a rise of 2 percentage points, but it is a 20% increase. Reports often blur the two, so check which one a figure refers to before acting on it.

Common Mistakes with Percentages

Percentages measured against different bases cannot simply be added: a 20% fall followed by a 20% rise leaves you at 96% of the starting value, not 100%. Discounts compound in the same way — 10% off and then a further 10% off is 19% off, not 20%. Always confirm which amount is the base (the "of" number) and whether the rate applies to the original or the already-adjusted value.

Frequently Asked Questions

How do I calculate a percentage of a number?: Multiply the number by the percentage and divide by 100: 20% of 80 = 80 × 20 ÷ 100 = 16.
How do I express a value as a percentage of another?: Divide the part by the whole and multiply by 100: 30 out of 120 → 30 ÷ 120 × 100 = 25%.
What is the difference between a percentage point and a percent?: A percentage point is the absolute difference between two percentages; a percent change is the relative difference. Going from 10% to 12% is +2 percentage points, which is also a +20% change.
Can I work backwards to the original number?: Yes. If you know the result and the rate, divide the result by the rate: a price of 54 after a 10% discount started at 54 ÷ 0.9 = 60, and a value of 46 after a 15% increase started at 46 ÷ 1.15 = 40.
Can a percentage be higher than 100%?: Yes. Doubling is a 100% increase and tripling is a 200% increase. Only a part of a whole — a test score or a market share, for example — is capped at 100%.