How to calculate percentage increase
Subtract the original number from the new number. Divide by the original value and multiply by 100. For a positive original number, use this standard percentage increase formula:
For a negative original value, this calculator divides by the absolute magnitude of the original to show signed change. This is a chosen convention, not the same as the conventional formula that divides by the signed original. Starting from zero makes a relative percentage change undefined.
Examples of percentage change
| Original | New | Result |
|---|---|---|
| 80 | 100 | 25% increase |
| 100 | 80 | 20% decrease |
| 150 | 165 | 10% increase |
How to add or subtract a percentage
To increase 100 by 10%, calculate 100 × (1 + 10 ÷ 100) = 110. To reduce it by 10%, use 100 × (1 − 10 ÷ 100) = 90. Choose Add / subtract above to enter your own number and rate.
Reverse percentage: find the original value
To find the original number before a percentage increase or decrease, divide the final number by (1 + rate ÷ 100). For example, a final value of 110 after a 10% increase started at 100. You cannot uniquely reverse a 100% reduction, because every original value becomes zero.
How to find what percentage one number is of another
Divide the part by the whole and multiply by 100. For example, 25 out of 200 is 12.5%. The whole cannot be zero.
Percentage increase in Excel
If cell A2 contains an original value and B2 the new value, enter =(B2-A2)/A2 in C2 and format the cell as a percentage. This standard spreadsheet formula assumes A2 is not zero; negative starting numbers can be interpreted differently from our absolute-denominator display.
Percentage points vs. percentage change
Moving from 20% to 25% is an increase of 5 percentage points, but a 25% relative increase (5 divided by 20). They are not interchangeable.
Frequently asked questions
What is the percentage increase from 80 to 100?
(100 − 80) ÷ 80 × 100 = 25%.
Can a percentage increase be negative?
Yes. A negative result describes a decrease when the original value is positive.
What if the starting number is zero?
The change in amount can still be calculated, but the relative percentage change is undefined because division by zero is not possible.
Related calculators
Calculating a raise at work? Use the pay raise calculator. To project your annual salary over several years, use the future salary calculator.