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Percentage Calculator

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Find a percentage of a number, work out percentage change and more.

What is the Percentage Calculator?

A percentage calculator works out three of the most common percentage problems: finding a percentage of a number, calculating percentage increase or decrease between two values, and finding what percentage one number is of another. To find X% of a number, multiply the number by X and divide by 100 (or multiply by X as a decimal). To find percentage change, subtract the original value from the new value, divide by the original value, then multiply by 100 — a positive result is an increase, a negative result a decrease. To find what percentage one number is of another, divide the first by the second and multiply by 100. "Percentage points" and "percent change" describe different things and are a common source of confusion — a rate rising from 4% to 5% is 1 percentage point but a 25% relative increase.

How it works

"Percentage" simply means "per hundred," so finding X% of a number means multiplying that number by X divided by 100. Percentage change — how much a value has increased or decreased — is a different calculation: it's the difference between the old and new value, divided by the old value, then multiplied by 100. These are two of the most common calculations people need, and mixing up which one to use for a given question is a frequent source of errors.

UK context

A particularly common confusion is between percentage change and percentage points. If a discount goes from 10% to 15%, that's a 5 percentage point increase, but it's a 50% increase in the size of the discount itself (5 ÷ 10 × 100) — both descriptions are technically correct, but they mean very different things, which matters a lot when comparing prices, interest rates, or statistics reported in the news.

Tips

When working out a percentage increase or decrease, always divide by the original (starting) value, not the new one — dividing by the wrong figure is the most common percentage-change mistake.
"Percentage points" and "percent change" are not interchangeable — check which one a source is actually describing, especially with interest rates, tax rates or survey results.
For quick mental maths, 10% of a number is easy to find by moving the decimal point one place — useful as a sense-check against a calculated answer.

Frequently asked questions

How do I calculate a percentage of a number?

Multiply the number by the percentage, then divide by 100 (or equivalently, multiply by the percentage expressed as a decimal). For example, 20% of 150 is 150 × 0.20 = 30.

How do I calculate percentage increase or decrease?

Subtract the original value from the new value, divide the result by the original value, then multiply by 100. A positive result is a percentage increase; a negative result is a percentage decrease.

What's the difference between percentage change and percentage points?

Percentage change is a relative measure (e.g. a rate rising from 4% to 5% is a 25% increase). Percentage points measure the absolute difference between two percentages (that same change is a 1 percentage point rise). They describe the same change differently, and mixing them up changes the meaning significantly.

How do I work out what percentage one number is of another?

Divide the first number by the second number, then multiply by 100. For example, to find what percentage 30 is of 150, calculate (30 ÷ 150) × 100 = 20%.