How to calculate percentage change

Percentage change compares a new value with its original value. It answers how large the change is relative to where you started.

The formula

Subtract the original value from the new value, divide that difference by the original value, then multiply by 100: ((new − original) ÷ original) × 100.

Percentage increase example

If a monthly cost rises from 80 to 100, the difference is 20. Divide 20 by 80 and multiply by 100 to get 25% increase. The calculation uses 80 because it is the starting amount.

Percentage decrease example

If the cost falls from 100 to 80, the difference is −20. Divide −20 by 100 and multiply by 100 to get 20% decrease. Reversing the direction changes the denominator, so a 25% increase from 80 to 100 and a 20% decrease from 100 to 80 are both correct.

When the original is zero

A standard percentage change is undefined when the original value is zero because division by zero is not possible. You can still report the absolute difference. The calculator accepts a positive original value and a new value of zero or greater; it does not interpret negative values.

Percentage points are different

When a rate moves from 20% to 25%, that is a change of 5 percentage points. The relative percentage increase is 25% because (25 − 20) ÷ 20 × 100 = 25%. Say which measure you mean when comparing rates.