How to use
- Enter the old value (the starting point) and the new value. The percent change appears instantly; thousands separators are fine.
- Below it you also get the absolute change, the ratio, and the percent change needed to get back to the old value.
- If the values are themselves percentages — interest rates, market share, poll numbers — tick The values are percentages to see the difference in percentage points.
Formulas
| Value | Formula | 80 → 100 |
|---|---|---|
| Percent change | (new − old) ÷ |old| × 100 | +25% |
| Absolute change | new − old | +20 |
| Ratio | new ÷ old | ×1.25 |
| Change to get back | (old − new) ÷ |new| × 100 | −20% |
The same gap of 20 gives different percentages depending on the starting point: 80 to 100 is a 25% increase, while 100 to 80 is a 20% decrease.
Percent vs percentage points
When the values are already rates, the plain difference between them is measured in percentage points. A mortgage rate falling from 3.5% to 3.0% is a drop of 0.5 percentage points, or −14.29% in relative terms (0.5 ÷ 3.5). “Unemployment rose 1 point” and “unemployment rose 1%” are very different: 3% plus 1 point is 4%, but 3% plus 1% is 3.03%.
Common pitfalls
- A 50% fall followed by a 50% rise does not get you back. 100 → 50 → 75. Recovering from a halving takes +100%, which is what “Change needed to get back” shows.
- Percent change from zero is undefined. Going from 0 to 10 is not “infinite percent”; only the absolute change is meaningful.
- Negative starting values are divided by their absolute value so the sign shows direction: a loss shrinking from −100 to −50 is +50%.
- Growth over several years should be compounded, not averaged year by year. See the compound interest calculator for how compounding adds up.
FAQ
Is percent change the same as percentage difference?
No. Percent change has a direction and uses the old value as the base. Percentage difference compares two values without a “before” and “after”: |a − b| ÷ ((a + b) ÷ 2) × 100. For 80 and 100 that is 22.2%, versus a 25% change.
Does a 100% increase mean double?
Yes. +100% is twice the original, +200% is three times. To find what percent one number is of another, use the percentage calculator.