Percent Calculator
Percent Calculator — runs in your browser. Inputs are not stored.
Percentage calculator
Enter values, then press Calculate.
※ Calculated in the browser only. Input is not sent to a server.
How to use
- Choose a mode: B% of A, A is what % of B, or change rate (before → after).
- Enter numbers in the A and B fields. The default example is 10% of 100.
- In change-rate mode, enter the before value and the after value.
- Press Calculate to see the result and the inputs A and B.
- Price discounts and VAT-inclusive prices fit dedicated calculators better.
Key concepts: percentages, ratios, and change rates
A percent is a hundredths part of a base. “B% of A” is A × B ÷ 100; “A is what % of B” is A ÷ B × 100. Grades, share, discount rate, and month-on-month change use the same idea.
Change rate is (after − before) ÷ before × 100. If before is 0, you cannot divide. For discounted price and VAT, use the discount calculator and VAT calculator.
Example
10% of 100 is 10. 25 as a percent of 200 is 12.5%. From 80 before to 100 after is a +25% change rate. If you only need a sale price, put list price and discount rate in the discount calculator.
Related: Discount calculator · VAT calculator · Margin calculator
Frequently asked questions
How does the percent calculator get change rate?
(after − before) ÷ before × 100. If before is 0, it is not calculated.
What is the difference between B% of A and A is what % of B?
The first finds an amount or quantity; the second finds a ratio (%). Changing the radio also changes the field labels.
Can it do discount prices too?
Ratio math works. For discount amount, final price, and VAT, use the discount calculator.
Do decimal percents work?
Yes. You can enter 7.5% and similar decimals.
Is this the same as margin rate?
Money left versus selling price fits the <a href="/tools/marketplace-margin/">margin calculator</a> better.
Are inputs saved?
No. Calculation stays in the browser.
Last reviewed: 2026-09-04