Percentage change and percentage points: what is the difference?

Percentage points measure the difference between two percentages. Percentage change measures that difference relative to the starting value. A move from 40% to 50% is an increase of 10 percentage points, or a 25% relative increase.

The Office for National Statistics explains the percentage-point distinction. The EU data visualisation guide describes calculating change relative to the initial value.

A worked example

This example is illustrative. Suppose 40 out of 100 requests were completed on time in one period, and 50 out of 100 in the next. The on-time rate rises from 40% to 50%.

Comparison	Calculation	Result
Difference in percentage points	50 − 40	10 percentage points
Relative percentage change	(50 − 40) ÷ 40 × 100	25% increase

For the relative calculation, the starting value is 40, not 100. The difference of 10 is one quarter of that starting value, so the rate has increased by 25% relative to where it began.

You can calculate the same relative change using decimal proportions: (0.50 − 0.40) ÷ 0.40 × 100 = 25%. Keep the two inputs in the same form.

Which wording should you use?

Use percentage points to state how far apart the two rates are. Use percentage change to state how large the movement is compared with the starting rate.

For this example, a clear sentence is: “The on-time rate rose from 40% to 50%, an increase of 10 percentage points.” If the relative movement matters, add: “That is a 25% increase relative to the original rate.” Giving both original rates makes the comparison easier to check.

Conditions that matter

• Name the baseline. Reversing the example changes the relative result. A fall from 50% to 40% is a decrease of 10 percentage points and a 20% relative decrease: (40 − 50) ÷ 50 × 100 = −20%.
• Do not divide by zero. From 0% to 10%, the percentage-point increase is 10. The usual relative percentage-change formula is undefined because its denominator is zero. Report the original and new rates instead.
• Check what the percentages describe. Subtracting rates does not establish that the groups, periods or definitions are comparable. Here both periods use 100 requests; real comparisons should identify the underlying counts and any change in what is being measured.