Percentage Calculator
Calculate percentages instantly — find X% of Y, percentage change, reverse lookups, and more.
How to use
- Select a calculation mode using the tabs above.
- X% of Y — Enter a percentage and a number to find what that percentage equals.
- % Change — Enter a starting value and ending value to find the percentage increase or decrease.
- What % is X of Y — Enter two numbers to find what percentage the first is of the second.
- Reverse % — Enter a value and a percentage to find what the original whole number was.
- Results update on calculate. Use the Copy Result button to copy the answer to your clipboard.
About this Percentage Calculator
Percentage math trips people up most on percentage change vs. percentage of a value — a price that rises 20% then falls 20% does not return to the original price (it rises to 120%, then falls to 96% of the original, a net 4% loss), because the second 20% is calculated on the new, larger number. This tool covers four related but distinct calculations in one place: X% of Y, percentage change between two values, what percentage X is of Y, and reverse percentage (finding the original whole from a known part and percentage).
Percentage change vs. percentage points — a common mix-up
If a rate goes from 20% to 25%, that's a 5 percentage-point increase (25 − 20), but a 25% relative increase (a 5-point gain is one-quarter larger than the original 20). These numbers get used interchangeably in casual writing, but they answer different questions — the % Change tab on this page calculates the relative change, not the percentage-point difference, so if you need the point difference between two percentages, that's a plain subtraction, not this tab.
Rounding and a common input mistake
Results are rounded for display (typically to 4–6 decimal places, with trailing zeros trimmed) but calculated from the full-precision input values, so copying a displayed result back in as a new input can introduce tiny rounding drift over several steps. The most common input mistake on the % Change tab specifically is swapping the "From" and "To" values — entering the ending value as "From" flips the sign and inverts the percentage, so a genuine increase gets reported as a decrease of a different magnitude.