Percentage Change Calculator
Calculate the percentage increase or decrease between two values, with the step-by-step formula, the percent difference, and a reverse mode that finds the original value. Free and private.
Example: 100 to 120 is a 20% increase.
Example: 150 after a 25% increase came from 120.
+20%
Increase- Value change
- +20
- Percent difference
- 18.18%
- From to
- 100 to 120
- Difference: 120 - 100 = 20
- Divide by start: 20 / 100 = 0.2
- Percent: 0.2 x 100 = +20%
(120 - 100) / 100 x 100 = +20%
The change from 100 to 120 is a 20% increase.
When the starting value is negative, the formula divides by its absolute value.
The result is 0%, so the value did not change.
A 100% decrease means the value dropped to 0.
Percent difference measures the gap against the average of the two values, so it stays positive.
On this page
This percentage change calculator shows how much a value has increased or decreased, in percent. Enter the starting value and the final value, and the result updates as you type: the percentage change, the plain value change, and the formula worked out step by step.
How to use this calculator
- Enter the starting value, the number before the change.
- Enter the final value, the number after the change.
- Read the result. A positive percentage is an increase, a negative percentage is a decrease, and 0% means the value did not change.
- Use the example chips to load a common scenario in one click, or press Swap values to reverse the comparison.
What the result shows
Each calculation gives you four things:
- Percentage change. The main result, for example +20% or -25%.
- Value change. The plain difference, final value minus starting value.
- Percent difference. The gap measured against the average of the two values instead of the starting value. It is always positive.
- Steps. The formula in three short lines so you can check the arithmetic yourself.
The percentage change formula
Percentage change is (final value minus starting value) divided by the starting value, times 100:
percentage change = (final minus start) / start x 100
Example: a price goes from 100 to 120. The difference is 20. 20 divided by 100 is 0.2, and 0.2 times 100 is 20%. The price went up by 20%.
Example: daily production drops from 2345 units to 1870 units. The difference is -475. -475 divided by 2345 is about -0.20256, so production fell by about 20.26%.
Find the original value
The second mode works in reverse. Enter the final value and the percentage change, and the calculator finds the starting value:
original value = final value / (1 + percentage / 100)
Example: a jacket now costs 150 after a 25% decrease. 150 divided by (1 minus 0.25) is 150 divided by 0.75, which is 200. The original price was 200.
Negative starting values
When the starting value is negative, the formula divides by its absolute value. A temperature that falls from -20 degrees to -45 degrees changes by (-45 + 20) / 20 x 100, which is -125%. The value moved 125% of its starting distance from zero.
Percentage change and percent difference
These two numbers answer different questions. Percentage change compares against the starting value, so 100 to 150 is +50%, while 150 to 100 is -33.33%. The same move in opposite directions is not the same size. Percent difference compares against the average of the two values, so it is symmetric: both orders give 40%.
Use percentage change when you care about growth from a base point. Use percent difference when you only care how far apart the two values are.
Limits
- The starting value cannot be 0, because there is no base to compare against.
- In the original value mode, a change of exactly -100% always ends at 0, so no single starting value can be recovered.
- Results are rounded to 6 decimal places.
- Everything is calculated in your browser. Nothing is sent to a server.