The percentage change formula
Subtract the original value from the new value. Divide that difference by the absolute original value, then multiply by 100.
(New − Original) ÷ |Original| × 100
A positive result means the value increased. A negative result means it decreased.
Example of a percentage increase
Website sign-ups increased from 320 to 400.
- Find the change: 400 − 320 = 80.
- Divide by the original: 80 ÷ 320 = 0.25.
- Convert to percent: 0.25 × 100 = 25%.
Sign-ups increased by 25%.
Example of a percentage decrease
A monthly expense fell from $250 to $210.
- Find the change: $210 − $250 = −$40.
- Divide by the original: −40 ÷ 250 = −0.16.
- Convert to percent: −0.16 × 100 = −16%.
The expense decreased by 16%.
Why the direction changes the answer
A move from 80 to 100 is a 25% increase because the 20-point difference is one quarter of 80. The reverse move from 100 to 80 is a 20% decrease because the same 20-point difference is one fifth of 100.
What if the original value is zero?
The formula would require division by zero, so there is no finite percentage change. You can report the absolute change instead—for example, “the value rose from 0 to 10”—but assigning a conventional finite percentage would be misleading.
Negative original values
Negative baselines require context. This site's calculator divides by the absolute original value so the result's sign follows the numerical direction of movement. In accounting, science, or analytics, check whether your field uses a different convention.
Percentage change vs. percentage difference
Use percentage change when one value is the established starting point. Use percentage difference when comparing two values symmetrically and neither one is the baseline.