How to increase a number by a percentage
The quickest method is the multiplier: add the percentage to 100, turn it into a decimal, and multiply once.
Increasing 250 by 15% becomes 250 × 1.15 = 287.5. One multiplication, no separate adding-on step, and it works for any percentage including rises over 100%.
Worked examples
The mistake to avoid: reversing an increase
Undoing a percentage increase is not the same as subtracting the percentage. If a price rose 15% to £287.50, the original is 287.50 ÷ 1.15 = £250.00. Subtracting 15% of £287.50 gives £244.38, which is wrong, because the 15% was calculated on the smaller starting number, not the final one. Always divide by the multiplier to go backwards.
The same logic is why removing VAT means dividing by 1.20 rather than knocking 20% off. Our VAT calculator handles that exact case.
Frequently asked questions
How do I increase a number by a percentage?
Multiply the number by 1 plus the percentage as a decimal. To increase 250 by 15%, multiply 250 × 1.15 = 287.5. The multiplier method is quicker and less error-prone than working out the percentage separately and adding it on.
How do I work out a pay rise?
Multiply your current salary by 1 plus the rise as a decimal. A 6% rise on £32,000 is 32,000 × 1.06 = £33,920. For the monthly difference, divide the increase (£1,920) by 12, which is £160 a month before tax.
How do I reverse a percentage increase?
Divide by the multiplier rather than subtracting the percentage. If a price is £287.50 after a 15% increase, the original was 287.50 ÷ 1.15 = £250. Subtracting 15% of £287.50 would give the wrong answer.
Can I increase a number by more than 100%?
Yes. An increase of 150% means the value grows to 2.5 times its original size, because the multiplier is 1 + 1.50 = 2.5. So 40 increased by 150% is 100.
What is the difference between percentage increase and percentage change?
A percentage increase applies a known percentage to a starting number to get a new value. Percentage change works in the other direction: you know both values and want to find the percentage between them. Use our percentage change calculator for that.