Percentage Increase and Decrease

Percentage change tells you how much a value has changed compared with its original value. It is useful for marks, scores, prices, measurements and everyday calculations.

Percentage increase formula

Percentage increase = ((new value − original value) ÷ original value) × 100

Example: a score rises from 60 to 75. The increase is 15, and 15 ÷ 60 × 100 = 25%. The score increased by 25%.

Percentage decrease formula

Percentage decrease = ((original value − new value) ÷ original value) × 100

Example: a score drops from 80 to 68. The decrease is 12, and 12 ÷ 80 × 100 = 15%. The score decreased by 15%.

Why the original value matters

The original value is the reference point. A change from 50 to 60 is a 20% increase, while a change from 60 to 70 is a 16.67% increase even though both changes are 10 points.

Percentage change is not the same as percentage points

Moving from 70% to 80% is a 10-percentage-point increase. Relative to the original 70%, it is a 14.29% increase. Use the wording that matches the question.

Common mistakes

Dividing by the new value instead of the original value.
Confusing a percentage-point change with a relative percentage change.
Rounding before completing the calculation.
Using the percentage-from-marks formula when the question asks for change.