What types of percentage calculations does the tool support?

The tool supports: X% of Y, what percentage is X of Y, and percentage change from X to Y. All three common percentage calculation types are covered.

Is my data sent to a server?

No. All calculations run entirely in your browser using JavaScript.

Can I calculate VAT or sales tax?

Yes. Use the percentage of a number calculator, enter the pre-tax amount and the tax rate to get the tax amount, then add it to the original for the total.

How do I calculate a percentage decrease?

Use the percentage change calculator. If the new value is less than the original, the result will be negative, showing the percentage decrease.

Percentage calculator

Percentage calculator is a calculator tool that solves the three most common percentage problems. It computes X% of Y, finds what percent X is of Y, and measures percentage change between two values, showing the formula alongside the result. The tool runs in your browser.

Percentage (%)Of number

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Calculation modes

Direct links for each type of percentage calculation.

What is X% of Y?

Calculate what X percent of a number is. Instant result with formula shown. Free, in-browser percentage calculator.

X is what % of Y?

Find what percentage one number is of another. Instant result with formula. Free in-browser calculator.

Percentage change calculator

Calculate percentage increase or decrease between two values. Shows the exact change and direction. Free, in-browser.

How to calculate a percentage

Choose the calculation type, percentage of a number, percentage change, or what percentage one number is of another.
Enter the values into the appropriate fields.
The result updates instantly as you type.
Click "Copy" to copy the result to your clipboard.

Common uses

Calculating discounts and sale prices when shopping
Working out percentage change between two values for reports or data analysis, use date calculator to find the time span between the two measurements
Finding what percentage a part is of a whole for statistics or grades. The unit converter can help when the values are in different measurement systems

Technical specification

Algorithm or formula: Three modes of pure arithmetic. X% of Y: (X/100) * Y. X is what % of Y: (X/Y) * 100. Percentage change from A to B: ((B - A)/A) * 100.
Browser API or library: Pure JavaScript Number arithmetic; no external library.
Input limits: Any IEEE 754 double-precision float; effective range roughly ±1.8e308 with ~15 significant digits of precision.
Output: Numeric result displayed alongside the calculation formula. Copyable to clipboard.
Known limitations: "X is what % of Y" returns NaN or infinity when Y is zero. Standard floating-point rounding applies to repeating decimals.

Frequently asked questions

What types of percentage calculations does the tool support?: The tool supports: X% of Y, what percentage is X of Y, and percentage change from X to Y. All three common percentage calculation types are covered.
Is my data sent to a server?: No. All calculations run entirely in your browser using JavaScript.
Can I calculate VAT or sales tax?: Yes. Use the percentage of a number calculator, enter the pre-tax amount and the tax rate to get the tax amount, then add it to the original for the total.
How do I calculate a percentage decrease?: Use the percentage change calculator. If the new value is less than the original, the result will be negative, showing the percentage decrease.

Reviewed and tested May 25, 2026.