Percent change calculator
Calculator
The calculator needs JavaScript. The tables below give the same numbers for common cases.
How it is worked out
- Subtract: 100 − 80 = 20.
- Divide by the starting value: 20 ÷ 80 = 0.25.
- Multiply by 100: 25%.
| Inputs | Answer |
|---|---|
| 800000, 1000000 | From 800,000 to 1,000,000 is a 25% increase. |
| 100, 80 | From 100 to 80 is a 20% decrease. |
| 50, 75 | From 50 to 75 is a 50% increase. |
How to use it
Percent change = (new − old) ÷ |old| × 100. A positive answer is an increase, a negative answer a decrease. From 80 to 100 the change is 20 ÷ 80 = 25%.
The starting value must not be 0, because a change from zero has no percent. Going up by 25% and then down by 25% does not return to the start: the second step is a percent of a larger number.
Frequently asked questions
What is the percent change from 80 to 100?
(100 − 80) ÷ 80 × 100 = 25%, an increase.
How do I find a percent decrease?
Use the same formula; a negative result is a decrease. From 100 to 80 it is −20%.
Why is the old value the base?
Because the change is measured against where you started.
Method: standard arithmetic shown step by step; no outside data is used. Checked 2026-11-12.
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General information only. Results are plain arithmetic on the numbers you enter; check anything important (money, health, school work) against your own records or the official source.