To find a percentage increase, subtract the original value from the new value, divide by the original and multiply by 100. To increase a number by a percentage, multiply it by 1 plus the percentage divided by 100: increasing 150 by 20% gives 150 × 1.2 = 180.
Formulas
% increase = (new − original) ÷ original × 100new value = original × (1 + % ÷ 100) Examples
- Rent rises from 1,200 to 1,290: (1,290 − 1,200) ÷ 1,200 × 100 = 7.5% increase.
- Add 15% to a price of 60: 60 × 1.15 = 69.
Common mistakes
- Undoing an increase with the same percentage. After +25% you need −20% to get back, not −25%.
- Confusing percent with percentage points: a rate going from 4% to 5% rises 1 point, which is a 25% increase.
In Excel and Google Sheets
- Increase from A2 to B2 (format as %)
=(B2-A2)/A2 - Increase A2 by the % in B2
=A2*(1+B2)
FAQ
How do I add a percentage to a number?
Multiply the number by 1 plus the percentage as a decimal. To add 20% to 150: 150 × 1.2 = 180.
How do I undo a percentage increase?
Divide by the same factor: 180 ÷ 1.2 = 150. The reverse percentage calculator does it for you.
What is a 100% increase?
Doubling. A 100% increase on 50 gives 100, and a 200% increase triples it to 150.
How we calculate: exact decimal math (no rounding errors), you choose the decimal places, and your numbers never leave your browser. Methodology →
Updated October 2026