Percentage Change Calculator
Percent change and difference from an old value to a new value.
How it works
Change = (new − old) ÷ old × 100%
Percent change measures relative increase or decrease: positive means up, negative means down.
If the old value is 0, the relative change is undefined (division by zero).
FAQ
Is it unchanged if it rises then falls back?
No. Up 50% then down 50% leaves 75% of the original, because the drop applies to a higher base.
Worked example
From 80 to 100: (100 − 80) ÷ 80 × 100% = +25%.
From 100 to 80: (80 − 100) ÷ 100 × 100% = −20%.
Note: +25% then −20% returns to 80, while −20% then +25% returns to 100 — the base differs by direction.
Notes and limitations
The gain needed to recover always exceeds the loss (a 50% drop needs a 100% gain). Compare rates in percentage points and describe relative change in percent; mixing them is a common source of misleading claims.