Percentage Increase Calculator
Enter where you started and where you ended up. We work out how much it grew in percent, and you can also use the same tool to raise a number by a set percentage.
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The formula
Percentage increase = ((New value - Old value) / Old value) x 100
How percentage increase works
You take the difference between the new and old value, divide it by the old value, and turn the result into a percentage. The old value always goes on the bottom because the question being asked is "how big is the change compared with where I began?".
If the answer comes out negative, the number actually fell. The calculator will tell you it is a decrease instead of showing a confusing minus sign.
A worked example
Rent goes from 1,200 to 1,350 a month. The difference is 150. Divide 150 by 1,200 and you get 0.125, so rent rose by 12.5%.
To go the other way and raise a number, choose "Increase X by Y%". Raising 1,200 by 12.5% gives 1,200 x 1.125 = 1,350.
Where people use it
- Pay rises and price changes
- Website traffic, sales and subscriber growth
- Investment returns over a period
- Comparing this year with last year in a report
Watch out for a zero start
If the old value is zero, a percentage increase cannot be calculated, because you would be dividing by zero. Growth from nothing is simply "new". In reports, people usually write "n/a" or show the absolute change instead.
Examples to check
Type these into the calculator above to see how it behaves. Every result below was produced by the same calculator code that runs on this page.
| What you enter | What you get |
|---|---|
| Percentage change from X to Y; Starting value (X): 80; New value (Y): 100 | Percentage increase: 25% |
| Percentage change from X to Y; Starting value (X): 1200; New value (Y): 1350 | Percentage increase: 12.5% |
| Percentage change from X to Y; Starting value (X): 45; New value (Y): 60 | Percentage increase: 33.3333% |
| Percentage change from X to Y; Starting value (X): 250; New value (Y): 200 | Percentage decrease: 20% |
Percentage Increase Calculator: frequently asked questions
What is the difference between percentage increase and percentage difference?
Percentage increase has a direction: it measures change from an old value to a new one. Percentage difference compares two numbers with no "before" and "after", so it divides by their average instead.
How do I add a percentage to a number?
Multiply the number by 1 plus the percentage as a decimal. To add 8% to 250, multiply by 1.08 and you get 270.
How do I turn a percentage into a decimal?
Divide by 100, or move the decimal point two places to the left. So 15% is 0.15, 5% is 0.05 and 120% is 1.2. Multiplying by that decimal is exactly how every percentage calculation works.
Can a percentage be more than 100?
Yes. 150% of a number is one and a half times that number. Percentages above 100 show up all the time with growth: if sales went from 40 to 100, they grew by 150%.
Why does a 50% rise followed by a 50% fall not bring me back to where I started?
Because the second percentage is taken from a bigger number. Start at 100, rise 50% to 150, then fall 50% and you land on 75. The same trap catches people with investments and sale prices.
How accurate is this calculator?
It uses standard double-precision arithmetic, accurate to about 15 significant digits. Results are rounded only for display.
Last reviewed: October 3, 2026