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Percentage Calculator

Calculate X% of Y, what percent X is of Y, or the percent change from X to Y.

How this calculator works

Choose which of the three common percentage questions you’re asking, enter your two numbers, and get the answer. For percent change, you’ll also get a clear increase/decrease label.

The formula

X% of Y            = (X / 100) × Y
X is what % of Y   = (X / Y) × 100
% change (X to Y)  = ((Y − X) / |X|) × 100
(positive = increase, negative = decrease; uses |X| so the sign
 stays correct even when X itself is negative)

Worked example

Percent change from 50 to 75:

  • (75 − 50) ÷ |50| × 100 = 25 ÷ 50 × 100 = +50% (an increase)

Frequently asked questions (FAQ)

What's the difference between a percentage point and a percent difference?

A percentage point is a simple difference between two percentages (going from 20% to 25% is a 5 percentage-point increase). A percent difference (or percent change) expresses that same move relative to the starting value: the same move is a 25% increase (5 ÷ 20 = 25%). Mixing the two up is a very common source of confusion.

How do I calculate a reverse percentage (finding the original number)?

If you know a result and the percentage, use the "X is what % of Y" mode in reverse: enter your known result as X and solve for what Y would need to be, or rearrange algebraically as Y = X ÷ (percent/100).

Why is my percent change negative?

A negative result in "% change from X to Y" mode means Y is smaller than X: a decrease. This calculator uses the starting value's absolute value in the formula so the sign always correctly reflects the direction of change, even when your starting number is negative.

Can a percentage be greater than 100%?

Yes. In "X% of Y" mode, entering more than 100% just means you're calculating more than the whole of Y (150% of 50 is 75). In "X is what % of Y" mode, a result over 100% simply means X is larger than Y.

How do I calculate percentage change with negative numbers?

This calculator handles it for you automatically: the "% change" mode divides by the absolute value of the starting number, so a move from a negative number toward zero (or a positive number) is always correctly reported as an increase, and vice versa.

Sources

This is standard arithmetic; no external source is needed.