Reverse Percentage Calculator

Recover an original amount from the final amount and a known increase or decrease.

Your inputs

Use consistent units and periods. Defaults are examples.

Check the assumptions below before relying on a result.

Original amount = final amount ÷ (1 + signed percentage change ÷ 100). Change amount = final − original.

A final amount of 120 after a 20% increase came from 100. A sale price of 80 after a 20% decrease also came from 100.

Measure an increase or decrease relative to a starting value.

Compare two non-negative values symmetrically using their average as the denominator.

Show the absolute difference between rates alongside the relative percent change.