How it works
"Percentage" covers three different questions that all use the same underlying idea — a percent is just a fraction out of 100 — but rearrange it differently depending on which value you're missing.
X% of Y = (X ÷ 100) × Y
X is what % of Y = (X ÷ Y) × 100
change by X% = Y × (1 + X ÷ 100)
Worked example
20% of 150.
- Divide the percent by 100: 20 ÷ 100 = 0.2.
- Multiply by the number: 0.2 × 150 = 30.
20% of 150 is 30.
Common questions
How is this different from the Percentage Change Calculator?
Percentage Change starts from two known values and asks how big the gap between them is, as a percent. This page's third mode goes the other direction: you already know the percent and the starting value, and want the new number after that change.
Can percent change ever be negative?
Yes — enter a negative percent change to see a decrease. −20% on 150 gives 150 × 0.8 = 120, twenty percent less than where you started.
Why can "X is what % of Y" go above 100%?
If X is larger than Y, the result is naturally over 100% — 150 is 150% of 100, for example. That's expected, not an error.