Percentage Change Calculator
Find the percentage increase or decrease from an original value to a new value. Enter the old and new numbers to get the signed percent change.
Last updated: October 2026
Percentage change
25 %
Formula below · 2 sources (mathsisfun.com, khanacademy.org) · Updated Oct 2026
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About this calculator
Percentage change tells you how much a value grew or shrank compared with where it started:
percentage change = (new value − original value) ÷ |original value| × 100
A positive result is an increase and a negative result is a decrease. The default inputs, 80 → 100, give (100 − 80) ÷ 80 × 100 = +25%.
Why the original value goes underneath
The change is measured against the starting point. A $10 rise on a $20 item is a 50% increase; the same $10 on a $1,000 item is 1%. Dividing by the absolute value of the original keeps the sign meaningful when the original is negative: going from −50 to −40 is shown as +20%, an increase.
Things that trip people up
Percentage changes do not cancel. A 50% rise from 100 gives 150, and a 50% fall from 150 gives 75, not 100, because the second change is taken from a bigger base. The table below shows the gain needed to undo a loss. If the original value is 0, the percentage change is undefined: there is no base to compare against, so report the absolute change instead. And a change between two percentages (an interest rate going from 4% to 5%) is 1 percentage point but a 25% change; this calculator gives the 25%.
| Loss | Gain needed to get back to the start |
|---|---|
| −10% | +11.1% |
| −20% | +25% |
| −25% | +33.3% |
| −33.3% | +50% |
| −50% | +100% |
| −75% | +300% |
How to use
Enter the starting value as the original and the later value as the new value. Example 1: a price rises from $80 to $100. (100 − 80) ÷ 80 × 100 = +25%. Example 2: monthly visitors fall from 200 to 150. (150 − 200) ÷ 200 × 100 = −25%, a 25% decrease. Example 3: a stock drops from $50 to $40 and then recovers to $50. The drop is (40 − 50) ÷ 50 × 100 = −20%; the recovery is (50 − 40) ÷ 40 × 100 = +25%.
Frequently asked questions
How do I calculate percentage change?
Subtract the original value from the new value, divide by the original value, and multiply by 100. From 80 to 100: (100 − 80) ÷ 80 × 100 = 25%. A negative answer means the value went down.
What is the difference between percentage change and percentage points?
Percentage points are the plain difference between two percentages; percentage change is relative. If a rate goes from 4% to 5%, it rose 1 percentage point, which is a 25% change because 1 is a quarter of 4.
Why doesn't a 50% gain undo a 50% loss?
Each percentage is taken from a different base. 100 falls 50% to 50; a 50% gain on 50 only brings it to 75. To get back to 100 you need a 100% gain. In general a loss of L needs a gain of L ÷ (1 − L) to recover.
Is percentage change the same as percentage difference?
No. Percentage change has a clear before and after and divides by the original value. Percentage difference compares two values with no direction and divides by their average, so 80 and 100 differ by 20 ÷ 90 × 100 ≈ 22.2%.
How do I find the original value from the new value and the percent change?
Divide the new value by (1 + change as a decimal). If something is 150 after a 25% increase, the original was 150 ÷ 1.25 = 120. After a 20% decrease to 80, the original was 80 ÷ 0.80 = 100.
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