Percentage of a Number Calculator — what is X% of Y

How it works

Taking a percentage of a number means finding that share of it. Since the symbol % stands for 0.01, a percent is really just a decimal in disguise: 15% is 0.15, 8.25% is 0.0825, 150% is 1.5. Convert the percent to its decimal and multiply by the number:

amount = (percent ÷ 100) × number

The ÷ 100 turns the percent into that decimal fraction, and multiplying scales the number by it. This is the everyday operation behind tips, sales tax, discounts and commissions — anywhere you need "this much of that".

Worked example

What is 15% of 80?

amount = (15 ÷ 100) × 80 = 0.15 × 80 = 12

The same recipe covers the common cases: a 20% tip on 250 is 0.20 × 250 = 50; 8.25% tax on 100 is 0.0825 × 100 = 8.25; and 100% of 50 is just 50, because 100% is the whole thing. Percentages above 100% give more than the number — 150% of 80 is 1.5 × 80 = 120.

Frequently asked questions

How do I find a percentage of a number?

Move the percent's decimal point two places left to get its decimal form, then multiply by the number. For 30% of 150: 30% is 0.30, and 0.30 × 150 = 45. That's the same as (30 ÷ 100) × 150.

How do I add or subtract a percentage, like tax or a discount?

Work out the percentage amount, then add or subtract it. A 20% tip on a $250 bill is 0.20 × 250 = $50, for a $300 total. A 30%-off discount on an $80 item is 0.30 × 80 = $24 off, leaving $56. A quick shortcut: paying after a 30% discount is paying 70%, so 0.70 × 80 = $56 directly.

Can I take more than 100% of a number?

Yes — percentages over 100% just mean more than the whole. 150% of 80 is 1.5 × 80 = 120, and 200% of a number is double it. This is common with growth ("sales were 250% of last year's") and markups.

How is this different from "what percent is A of B"?

This calculator starts with a **percent** and a number and returns an **amount** (15% of 80 → 12). The reverse question — you have two numbers and want the percent between them (12 is what percent of 80?) — is the percentage calculator. They're inverses of the same relationship.

How do I calculate a percentage in my head?

Break it into easy pieces. 10% is just the number with the decimal point moved one place left (10% of 80 is 8), and 1% moves it two places (0.8). Build the rest from those: 20% is two 10%s (16), 5% is half of 10% (4), and 15% is 10% + 5% (8 + 4 = 12).

Does this work for percentages with decimals?

Yes — 8.25% is simply 0.0825, so 8.25% of 100 is 0.0825 × 100 = 8.25. The method doesn't care whether the percent is a whole number: convert it to its decimal form and multiply, exactly as with a round percentage.