Percentage Change Calculator
One calculator for movement in either direction, with the direction of travel spelled out.
Percentage change
Enter where the value started and where it ended.
Recent calculations
When to use percentage change
Percentage change is the general tool for before-and-after comparisons. Increase and decrease are just its two halves: feed it any pair of values and it works out both the size of the movement and its direction. This makes it the right choice when you do not know in advance which way a figure moved, such as when processing a column of monthly results.
It appears constantly in reporting — revenue against last quarter, traffic against last month, prices against last year — because it strips out the scale of the underlying numbers and leaves only the shape of the movement, which is what makes two different-sized series comparable.
How to use it
Put the earlier value in the first box and the later one in the second. The result names the direction, shows the raw difference alongside the percentage, and lists the steps. Order matters: swapping the boxes changes both the sign and the size of the answer, because the denominator changes too.
The formula
A positive result is an increase and a negative result is a decrease. The calculator shows the size of the change and states the direction in words, so there is no sign to misread.
Worked examples
A rise: website visits from 1,250 to 1,500
- 1,500 − 1,250 = 250
- 250 ÷ 1,250 = 0.2
- 0.2 × 100 = a 20% increase
A fall: fuel price from 108 to 94.50
- 94.50 − 108 = −13.50
- −13.50 ÷ 108 = −0.125
- −0.125 × 100 = a 12.5% decrease
Reading the result honestly
Two figures with identical percentage changes can tell completely different stories. A shop going from 2 sales to 3 has grown 50%, and so has a chain going from 200,000 to 300,000. Percentages hide the base, which is a feature when you want comparability and a trap when the base is tiny. Quote the underlying numbers alongside the percentage whenever the base is small.
Common mistakes
Averaging percentage changes. Three months of +10%, −10% and +10% do not average to +3.33%. Compounding them gives 1.1 × 0.9 × 1.1 = 1.089, an 8.9% rise overall.
Starting from zero. If the original value is zero, there is no percentage change to calculate — any growth from nothing is infinite in percentage terms. The calculator explains this rather than showing a meaningless result.
Comparing across inconsistent periods. A change measured over four weeks against one measured over a calendar month is not a like-for-like comparison, however precise the arithmetic.