How to calculate percentage and discount

Published 2026-10-23 · SmartCalc Converter

Percentages show up everywhere: sale tags, restaurant bills, exam marks and price rises. The good news is that nearly all of them use one idea.

What a percentage means

Percent means "out of 100". So 25% is 25 out of every 100, or one quarter. To find a percentage of a number, multiply the number by the percentage and divide by 100.

Finding a percentage of a number

What is 15% of 200? Multiply 200 by 15 to get 3,000, then divide by 100. The answer is 30. A quick shortcut is to find 10% by moving the decimal point one place, then add half of that for 5%. For 200, 10% is 20 and 5% is 10, so 15% is 30.

Working out a discount

A discount is a percentage you take away. A pair of shoes costs 80 and is 25% off. The discount is 80 × 25 ÷ 100 = 20, so you pay 80 − 20 = 60. You can also multiply by what remains: 75% of 80 is 60. Both routes give the same answer.

Adding a percentage

Tax, service charges and tips are added on top. A bill of 50 plus 5% tax is 50 + 2.50 = 52.50. Or multiply by 1.05 for the same result.

Going backwards: find the original price

If a coat costs 90 after a 25% discount, the original price is not 90 plus 25%. The 90 is 75% of the original, so divide 90 by 0.75 to get 120.

Common mistakes

• Adding discounts together. 20% off then 10% off equals 28% off, because the second discount applies to the smaller price.
• Mixing up the base. A rise from 50 to 60 is 20% of the old value, but a fall from 60 to 50 is only 16.7%, because the starting value is different.
• Forgetting to divide by 100. Check that your answer is sensible: 15% of 200 should be well under 200.

Quick mental tricks

You can do many percentages in your head. Ten percent is the number with the decimal point moved one place. Fifty percent is half and twenty-five percent is a quarter. Twenty percent is ten percent doubled, so 20% of 85 is 8.5 doubled, which is 17. Seventy-five percent is the whole minus a quarter. These shortcuts help you estimate before you check the exact answer with a tool.

Check your work in seconds

Use the percentage and discount calculator to confirm your answer. It has modes for a percentage of a number, a discounted price and an added percentage. You can also open the tool straight from the home page.

Try the calculator

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