How to use Percentage Calculator

Choose the question, for example What is A% of B?.
Enter both values; their meaning changes with the question.
Set the decimal places. The answer updates as you change the values.
Read the result and the equation under it.

Example: Percentage Calculator

Work out 12 percent of 250.

You add

Question What is A% of B?, percentage (A) 12, number (B) 250.

You get

12% of 250 is 30, shown with the equation line 12% of 250 = 30.

Options

What do you want to work out?: Six questions cover a percentage of a number, one number as a percent of another, percent change, increase, decrease and percent difference. Picking one relabels both value fields.
Decimal places: 0, 2, 4, 6 or 8 places. The result rounds half up at the chosen precision, and the equation shows the same figures.
First value (A) and Second value (B): The two numbers swap roles with the question. For a percent change, A is the starting value.

Supported inputs and limits

Values go up to 1,000,000,000,000,000 and may be negative. The whole (B) cannot be zero in A is what percent of B, and the starting value cannot be zero for a percent change, because that division has no answer. Enter 20 to mean 20%, not 0.20. Percent difference uses the mean of both values, so it differs from percent change. Results round at the decimal place you choose and are not formatted as currency.

Where your input is processed

This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.

Percentage points are not percentages

A rate moving from 20% to 25% has risen 5 percentage points, while the change relative to the starting value is 25%. Both are true and they answer different questions. The same base effect runs the other way: increasing 120 by 25% gives 150, but decreasing 150 by 25% gives 112.5, not 120, because the second calculation takes a quarter of 150.

Questions about Percentage Calculator

What is the difference between percentage change and percentage difference?

Change uses the starting value as its base; difference uses the mean of both values. From 100 to 120 is a 20% change but an 18.181818% difference.

Why is a change from zero undefined?

The formula divides by the starting value, and division by zero has no answer, so the tool refuses the calculation.

How do I take 15% off a price?

Use Decrease A by B%: 80 falls to 68. For the discount amount and the tax as well, use the Discount Calculator.

Pay rises from 20 to 25 an hour. Is that a 5% rise?

No. It is a rise of 5 in the hourly figure and a 25% increase. Mixing the two up is a common percentage mistake.

Project manager: Tony Hines · Content updated 29 September 2026 · Report a problem

Percentage Calculator

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