Percentage Calculator

The three percentage questions people actually ask, answered instantly. Everything runs locally in your browser.

New to this? Read the Percentage Calculator guide →

What is a percent of a number?

What is % of ?

= 30

One number is what percent of another?

is what % of ?

= 20%

Percentage increase or decrease

From to

= +20%

How to use the percentage calculator

Pick the kind of question you have, type in the two numbers, and read the answer. It handles the three calculations that cover almost every real-world percentage problem.

The three core calculations

What is X% of Y? e.g. 20% of 80 is 16. Multiply: Y × X / 100.
X is what percent of Y? e.g. 16 is 20% of 80. Divide: X / Y × 100.
Percentage change from X to Y. e.g. 80 to 100 is a 25% increase. Use (Y − X) / X × 100.

Everyday uses

Working out a sale discount or a sales-tax amount.
Figuring a tip, a commission or an interest figure.
Turning a test score into a percentage, or a price change into a percent.

A handy sanity check: "X% of Y" always equals "Y% of X", so 8% of 25 is the same as 25% of 8, which is 2.

Embed this on your site

Writing about discounts, margins, tips or statistics? Add a working percentage calculator to your own page — free, no signup, no tracking. Copy the snippet below into your HTML; the credit line is part of the deal.

<iframe src="https://andergrove.com/tools/percentage-calculator/embed/" title="Percentage Calculator" style="width:100%;max-width:720px;height:330px;border:1px solid #e2e8f0;border-radius:12px" loading="lazy"></iframe>
<p>Percentage Calculator by <a href="https://andergrove.com/tools/percentage-calculator/">Andergrove Software</a></p>

Where you'd use this

The everyday arithmetic people get wrong under time pressure: discounts, tips, tax, margins, and "what percentage is this of that".

For example: A jacket is marked 30% off, then a further 20% off at the till. That is not 50% — it is 0.7 × 0.8 = 0.56, a 44% discount. On a $200 jacket the difference is $12.

Common calculations

Frequently asked questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number — 15% of 80 is 0.15 × 80 = 12. The calculator does this and the reverse (what percent X is of Y) for you.

How do I find a percentage increase or decrease?

Subtract the old value from the new, divide by the old value, and multiply by 100. Use the dedicated increase and decrease modes for instant results.

Is my data uploaded?

No. Every calculation runs in your browser.