Calculators

Percentage Calculator

Work out a percentage of a number, what percentage one number is of another, or the percentage change between two values.

What is X% of Y?

X (percentage)

Y (number)

Result: —

X is what percentage of Y?

X (part)

Y (whole)

Result: —

Percentage increase / decrease

From

Change: —

How to use the percentage calculator

Pick the calculator that matches your question — all three are on this page.
Enter your numbers into the fields.
The result updates automatically as you type.

Features

Three common percentage calculations in one place
Results update live, no button to press
Handles negative and decimal values

Common percentage calculations

Use “percentage of a number” for questions such as 15% of 240, and percentage change when comparing an old value with a new one. A positive change means the value increased; a negative change means it decreased.

Percentage points are different from percent change. Moving from 20% to 25% is an increase of 5 percentage points, but the relative increase is 25%. Keeping those two ideas separate avoids a common reporting mistake.

For business reports, label the original value, new value and whether you are reporting a percentage or percentage-point difference. Clear labels make the result easier for someone else to reproduce and verify.

Frequently asked questions

We use ((new value − old value) / old value) × 100, which is the standard way to express percentage increase or decrease.

Percentage change is undefined when the starting value is zero, so the result field will show a dash instead of a number.

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Choose the right percentage question

“What is 20% of 80?”, “80 is what percent of 100?” and “what is the percentage change?” are different calculations. Select the form that matches the question before interpreting the result.

For percentage change, the starting value is the denominator.
A 50% rise followed by a 50% fall does not return to the original value.
Use enough decimal places for finance or measurement work, then round only at the end.