Percentage Calculations Explained Simply

What does percentage mean?

Percentage means “per hundred”. 25% means 25 out of every 100, which is the same as 0.25 or one quarter.

Turning a percentage into a decimal makes many calculations easier: divide the percentage by 100. For example, 7% becomes 0.07.

Want to try the idea yourself? Use the Percentage Calculator.

How to find a percentage of a number

Convert the percentage to a decimal and multiply it by the number. To find 15% of £80, calculate 0.15 × 80 = £12.

The same method works for discounts, tips, tax rates and many other everyday calculations.

If you want to explore this topic further, see How to Calculate VAT: Add or Remove VAT Easily.

How to find what percentage one number is of another

Divide the part by the whole, then multiply by 100. If 18 out of 24 people attended, 18 ÷ 24 × 100 = 75%.

Make sure you know which number is the whole. Reversing the two numbers gives a completely different result.

Percentage increase and decrease

To calculate percentage change, subtract the old value from the new value, divide the difference by the old value and multiply by 100.

If a price rises from £80 to £100, the increase is £20. £20 ÷ £80 × 100 = 25%. If it falls from £100 back to £80, that is a 20% decrease, not 25%, because the starting value is now £100.

Use the right percentage calculation

Percentage questions can sound similar while requiring different formulas. “What is 20% of 50?”, “20 is what percentage of 50?” and “what is the percentage change from 20 to 50?” are three different calculations.

The Percentage Calculator lets you choose the calculation you need and avoids having to remember each formula.