Percentage Change Calculator
Enter an original value and a new value to see the percentage increase or decrease between them, the absolute change in value, and the full working.
How to use this calculator
- Enter the original value — where the figure started, such as
120. - Enter the new value — where it ended up, such as
150. - Read the result above. The hero figure gives the percentage and says whether it is an increase or a decrease; the four figures beside it show the change in value, both inputs and the direction in words.
Both values must be in the same unit — compare two prices, two weights, two quantities or two scores, not one of each. Decimals and negative numbers are accepted. The calculation runs in the page as you type, and your figures are carried in the address bar so a result can be shared or bookmarked.
How percentage change is worked out
Percentage change compares the difference between a new value and an original value against the original value. A positive result is an increase; a negative result is a decrease.
- Original value — the figure you are measuring from
- New value — the figure you are measuring to
- |Original value| — its magnitude, so a negative starting value still gives a sensible direction
For ordinary positive values the bars make no difference, so the formula is usually written with the original value used directly: (New − Original) ÷ Original × 100. The absolute change is simply New value − Original value.
Worked example: a percentage increase
| Step | Value |
|---|---|
| Original value | 120 |
| New value | 150 |
| Change in value | 150 − 120 = 30 |
| Divide by the original value | 30 ÷ 120 = 0.25 |
| Convert to a percentage | 0.25 × 100 = 25% |
| Percentage change | 25% increase |
Worked example: a percentage decrease
| Step | Value |
|---|---|
| Original value | 500 |
| New value | 425 |
| Change in value | 425 − 500 = −75 |
| Divide by the original value | −75 ÷ 500 = −0.15 |
| Convert to a percentage | −0.15 × 100 = −15% |
| Percentage change | 15% decrease |
A decrease is shown as 15% decrease rather than −15% decrease: the word already carries the direction, so the extra minus sign only reads as a double negative. The signed form −15% appears in the working line under the inputs.
Why the original value matters
A rise from 100 to 150 is a 50% increase:
(150 − 100) ÷ 100 × 100 = 50%
But a fall from 150 back to 100 is a 33.33% decrease:
(100 − 150) ÷ 150 × 100 = −33.33%
Percentage increases and decreases are measured from different starting values, so an increase and an equal numerical decrease do not usually cancel each other out.
Starting from zero
Percentage change cannot be calculated from a starting value of zero, because the formula divides by the original value. When the original value is zero, the calculator shows the absolute change instead — a move from 0 to 50 reports a change of +50 and reports the percentage as not defined. When both values are zero it reports no change, without presenting a percentage.
Working with negative values
When either value is negative, the calculator uses the magnitude of the original value as the baseline. The change itself keeps its sign, so it still tells you whether the move was up or down.
| Step | Value |
|---|---|
| Original value | −100 |
| New value | −50 |
| Change in value | −50 − (−100) = 50 |
| Baseline magnitude | |−100| = 100 |
| Divide by the baseline | 50 ÷ 100 = 0.5 |
| Convert to a percentage | 0.5 × 100 = 50% |
| Percentage change | 50% increase |
Interpret negative-value results in the context of what the values represent.
Quick examples
| Original value | New value | Percentage change |
|---|---|---|
| 120 | 150 | 25% increase |
| 500 | 425 | 15% decrease |
| 80 | 100 | 25% increase |
| 100 | 100 | No change |
| 0 | 50 | Not defined |