How to use Percentage Calculator
- Pick the sum: percent of a number, what percent, percentage change, or add or subtract a percent.
- Type your two numbers. Commas, spaces and Arabic numerals are fine.
- Read the answer and the working underneath it.
- Copy the answer with one tap.
Why use Percentage Calculator
Shows the working
Every answer comes with its formula, so you can check it or use it in homework.
Percentage change
Increase or decrease between two values, with the direction spelled out.
VAT and discounts
Add or subtract a percentage, for example 15% VAT or 20% off.
Clean decimals
Results are rounded sensibly, without floating-point noise such as 0.30000000000000004.
About this tool
Percentages come up everywhere: discounts, VAT, exam marks, pay rises and interest. This calculator covers the four questions people ask most, and each one shows its formula so you learn the method as well as the answer.
Percentage change is measured from the starting value. Going from 80 to 100 is a 25% increase, but going back from 100 to 80 is a 20% decrease, because the starting value is different. The calculator always says which way the change goes.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 20% of 150 is 150 × 20 ÷ 100 = 30.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 out of 150 is 30 ÷ 150 × 100 = 20%.
How is percentage change calculated?
Subtract the old value from the new one, divide by the old value and multiply by 100. From 80 to 100: (100 − 80) ÷ 80 × 100 = a 25% increase.
How do I add VAT or take off a discount?
Choose "Add or subtract %". Adding 15% VAT to 200 gives 230; taking 20% off 200 gives 160.
Why does a 50% rise not undo a 50% drop?
A 50% drop takes 100 to 50. A 50% rise on 50 adds only 25, giving 75. Getting back to 100 needs a 100% rise.
How do I work out a percentage for grades or marks?
Choose “X is what %”, enter the marks you got as the part and the total marks as the whole. This percentage calculator works online in any browser, for free.