Guide1 min readUpdated June 25, 2026

How to calculate percentage change

Short answer

Percentage change is the difference between the new and old values, divided by the old value, times 100. From 80 to 100 is a (100 - 80) / 80 = 25 percent increase.

The formula

change % = (new - old) / |old| x 100

Percentage change

A positive result is an increase, a negative result is a decrease. Dividing by the original value is what makes it a relative change rather than a raw difference.

Worked examples

From 80 to 100: (100 - 80) / 80 = 0.25 = a 25 percent increase
From 100 to 80: (80 - 100) / 100 = -0.20 = a 20 percent decrease
From 50 to 150: (150 - 50) / 50 = 2.0 = a 200 percent increase

Increase and decrease are not symmetricA 25 percent rise followed by a 25 percent fall does not return to the start, because each percentage is taken from a different base. 100 up 25 percent is 125, then down 25 percent is 93.75.

Try it: Percentage CalculatorCalculate percentage change, percent of a number, and more locally.Open tool

References

Questions

What is the difference between percentage change and percentage points?

Percentage change is relative to the starting value. Percentage points are an absolute difference between two percentages: going from 10 percent to 15 percent is 5 percentage points, but a 50 percent increase.

Why divide by the old value and not the new one?

Percentage change measures growth relative to where you started, so the original value is the base. Dividing by the new value would answer a different question.

Does the percentage calculator store my numbers?

No. All calculations run locally in your browser and nothing is uploaded.