Percentage Calculator

Each mode is a rearrangement of the same relationship between a part, a whole, and a percentage. "X% of Y" multiplies Y by X÷100. "X is what % of Y" divides X by Y and multiplies by 100. "% Change" takes the difference between two values as a fraction of the starting value, so it correctly shows a decrease as negative.

Percent change is the one people most often get wrong by hand — going from 50 to 75 is a 50% increase, but going from 75 back to 50 is only a 33.3% decrease, because the base you're dividing by is different each time.