How to calculate percentage change

Percentage change tells you how much a value grew or shrank relative to where it started.

The formula

change % = (new − old) ÷ old × 100

A positive result is an increase, a negative one is a decrease.

Three examples

• Price rise. 80 to 100: (100 − 80) ÷ 80 × 100 = +25%.
• Price drop. 200 to 150: (150 − 200) ÷ 200 × 100 = −25%.
• Traffic growth. 1,200 to 1,800 visits: (1,800 − 1,200) ÷ 1,200 × 100 = +50%.

The mistake everyone makes

The base is always the old value. Going from 80 to 100 is +25%, but going back from 100 to 80 is −20%, not −25%. The two changes use different bases.

For the same reason, a 50% increase followed by a 50% decrease leaves you at 75% of where you started.

Percentage points are different

If a conversion rate moves from 2% to 3%, it rose by one percentage point, which is a 50% relative increase. Mixing these up is the quickest way to mislead a report.

Try it with the percentage calculator.