Percentage Calculator
Calculate percentages instantly with our free percentage calculator. Find a percentage of a number, work out what percentage one number is of another, or calculate percentage increases and decreases.
Find a percentage of a number
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Percentage calculation guide
Learn the formulas for percentages, percentage increase and discounts.
More practical guides
Calculate a percentage discount · Percentage increase and decrease
How to calculate percentages
Find a percentage of a number: divide the percentage by 100, then multiply by the number. For example, 25% of 80 = 0.25 × 80 = 20.
Find what percentage one number is of another: divide the part by the whole, then multiply by 100. For example, 20 ÷ 80 × 100 = 25%.
Percentage increase: subtract the original value from the new value, divide the difference by the original value, then multiply by 100. A rise from 80 to 100 is a 25% increase.
Percentage decrease: subtract the new value from the original value, divide the decrease by the original value, then multiply by 100. A fall from 100 to 80 is a 20% decrease.
Percentage increases and decreases are measured against the original value. That is why increasing a number by 20% and then decreasing the result by 20% does not return to the starting number.
How to use this tool
Enter the values for the percentage question you want to solve. UsefulFox calculates the result instantly for discounts, increases, decreases and everyday comparisons.
Percentage calculation examples
20% of 350: 0.20 × 350 = 70. 15% of £60: 0.15 × £60 = £9. 25% discount on £80: the discount is £20, so the sale price is £60.
How to calculate percentage change
For a change from an old value to a new value, use (new − old) ÷ old × 100. For example, an increase from 40 to 55 is 15 ÷ 40 × 100 = 37.5%. A decrease from 80 to 60 is 20 ÷ 80 × 100 = 25%.
How to work out a percentage discount
Multiply the original price by the discount percentage to find the saving, then subtract it from the original price. A 30% discount on £50 is £15, leaving a sale price of £35. To find the percentage discount when you know both prices, divide the saving by the original price and multiply by 100.
What can it be used for?
Use it for discounts, price changes, tips, exam scores, margins, growth rates and quick everyday calculations.
Frequently asked questions
1How do I find a percentage of a number?
Multiply the number by the percentage expressed as a decimal. For example, 20% of 50 is 10.
2How do I calculate percentage increase?
Find the difference between the new and original values, divide by the original value, then multiply by 100.
3How do I calculate percentage decrease?
Find how much the value fell, divide by the original value, then multiply by 100.
4Can I use this for discounts?
Yes. It is useful for checking sale prices, markdowns and mark-ups.
5What is the percentage increase from 40 to 55?
The increase is 15. Divide 15 by the original value 40 and multiply by 100: 15 ÷ 40 × 100 = 37.5%.
6Why does a 20% increase followed by a 20% decrease not cancel out?
Because the second percentage is calculated from a different starting value. 100 increased by 20% is 120; reducing 120 by 20% gives 96, not 100.