How to calculate percentage change

Work through increases, decreases and the special case of a zero starting value.

Percentage change compares a new value with its original value. With a positive original value, the formula is (new − original) / original × 100.

An increase

A quantity growing from 80 to 100 changes by (100 − 80) / 80 × 100 = 25%. Try it in the Percentage Change Calculator.

A decrease

From 100 to 80, the result is −20%. Reversing an increase does not produce the same percentage because the denominator changes.

Zero and negative starting values

An original value of zero has no finite relative percentage change. For negative originals, this calculator divides by the absolute original value and states that convention in its formula. Choose a definition appropriate to the data being described.

For a percentage of a single number, use the Percentage Calculator. Price reductions can be calculated with the Discount Calculator.