Percentage Calculator

Solve percentage of a number, percentage change, and percent increase/decrease instantly.

X% of Y

(X / 100) × Y

% of
50

X is what % of Y

(X / Y) × 100

is what % of
25%

% change from X to Y

((Y − X) / X) × 100

to
50%

X increased/decreased by Y%

X × (1 ± Y / 100)

± by%
+220 / −180

Find whole: X is Y% of what?

X / (Y / 100)

is% of what
200

About the Percentage Calculator

A percentage is just a fraction out of 100, and every calculation here is a variation on one relationship: part = (percent / 100) × whole. Rearranging which value is unknown gives the five modes on this page — solve for the part, the percent, the whole, or the new value after a percentage change or adjustment. For example, a $200 item marked up by 15% (X% of Y, then increase) becomes 200 × 1.15 = $230, and if that same $230 later drops back to $200, the percentage decrease isn't 15% but ((230 − 200) / 230) × 100 ≈ 13.04% — a common source of confusion since increase and decrease percentages between the same two numbers are never equal.

To use it: type into either input field of any panel and its result updates immediately — no submit button needed. Each of the five panels is independent, so you can work multiple percentage problems side by side (say, comparing a discount calculation against a year-over-year growth calculation) without your inputs interfering with each other, and copy just the result you need with its dedicated copy button.

What is percentage change?+

Percentage change from X to Y is ((Y − X) / X) × 100. A positive result is an increase; a negative result is a decrease.

What's the difference between "X% of Y" and "X is what % of Y"?+

"X% of Y" finds a portion of a number. "X is what % of Y" does the reverse — it tells you what share X represents of the whole Y.

Why is a 50% increase followed by a 50% decrease not back to the original number?+

Because each percentage applies to a different base. Increasing 200 by 50% gives 300; decreasing 300 by 50% gives 150, not 200 — the second percentage is taken from the new, larger number, not the original.

Can percentage change be negative or over 100%?+

Yes to both. A drop from 200 to 100 is a -50% change. A jump from 10 to 100 is a +900% change — percentage change has no upper bound since it's relative to the starting value.

What does "find the whole" actually solve?+

It answers questions like "60 is 20% of what number?" by rearranging the percentage formula to solve for the total: whole = part / (percent / 100). Useful when you know a portion and its share but need the original total.

Why does increasing then decreasing by the same percentage show two different results?+

The "increased/decreased by Y%" panel shows both outcomes side by side deliberately — X × (1 + Y/100) for the increase and X × (1 − Y/100) for the decrease — since they're genuinely different numbers, not two ways of writing the same answer.

How many decimal places does this calculator show?+

Results display up to 4 decimal places where relevant, formatted with locale-aware thousands separators, so you can see fractional-percent precision without excessive trailing digits.