Percentages explained simply

Percentages are everywhere: discounts, exam marks, interest, statistics. The idea is simple.

What does percent mean?

Percent means "out of 100". 25% means 25 out of every 100. Draw a 10 by 10 grid, shade 25 squares, and you have 25%. You can also write 25% as the fraction 25/100 = 1/4 or as the decimal 0.25. Explore it in the interactive lesson Percentages: parts of 100.

Three percentages you can do in your head

• 50% is half: divide by 2.
• 25% is a quarter: divide by 4.
• 10% is a tenth: divide by 10.

So 10% of 80 is 8, 25% of 60 is 15, and 50% of 90 is 45.

Build any percentage from 10%

• 20% = double 10%. 20% of 70 = 14.
• 5% = half of 10%. 5% of 80 = 4.
• 15% = 10% + 5%. 15% of 60 = 6 + 3 = 9.
• 30% = three lots of 10%.

Discounts

A jacket costs ₹800 and is 20% off. 10% of 800 is 80, so 20% is 160. The sale price is 800 − 160 = ₹640. You can also multiply by 0.8 (which is 100% − 20% = 80%).

Percentage increase

Increase 60 by 25%: 25% of 60 is 15, so the new value is 75. Or multiply by 1.25.

Percentage of a total

If you score 36 out of 40, divide 36 by 40 = 0.9, which is 90%.

Practise

Print free percentage of a number worksheets or percentage change worksheets, or practise on screen with Maths Practice.

Common questions

How do you calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. 15% of 200 is 0.15 × 200 = 30.

How do you turn a percentage into a decimal?

Divide by 100: 35% = 0.35. To go the other way, multiply by 100.

What is 10 percent of a number?

Divide by 10. For 10% of 450, the answer is 45.

What age do children learn percentages?

Simple percentages (50%, 25%, 10%) from about age 9 to 10, and percentage change from about age 11 to 13.

This guide is general information. For exams, follow your school, teacher and official exam board, and use your own judgement about what suits your child.