The Percentage Calculator solves the three percentage problems people actually run into: finding X% of a number, working out the percentage change between two values, and finding what percentage one number is of another โ€” all in one place.

Percentage Calculator

Calculate percentages, percentage change, and more.

%
of
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is what % of
Result
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The three calculations, worked out

1. X% of a number. “What is 15% of 80?” Convert the percent to a decimal (15% = 0.15) and multiply: 0.15 × 80 = 12. This is the calculation behind tips, discounts, and sales tax.

2. Percentage change. “A price went from $40 to $50 โ€” what’s the increase?” Subtract, divide by the original, then multiply by 100: (50 − 40) ÷ 40 × 100 = 25% increase. If the price had dropped from $50 to $40, the base changes to 50, giving a 20% decrease โ€” which is why increases and decreases between the same two numbers aren’t equal.

3. What percent is X of Y. “18 out of 24 โ€” what percentage?” Divide and multiply by 100: 18 ÷ 24 × 100 = 75%. This is how you turn a test score or a completed portion into a percentage.

Quick reference

Question Method Example โ†’ result
X% of Y (X ÷ 100) × Y 20% of 150 โ†’ 30
X is what % of Y (X ÷ Y) × 100 30 of 150 โ†’ 20%
% change A โ†’ B (B − A) ÷ A × 100 150 โ†’ 180 โ†’ +20%

The most common mistake

A percentage increase and the matching decrease do not cancel out. If a $100 item rises 20% to $120, then falls 20%, it does not return to $100 โ€” the second 20% is taken from $120, so it drops $24 to $96. Whenever you reverse a percentage change, the base has moved, so the two percentages differ. The calculator always applies each percentage to the correct base, which avoids this trap.

Where you’ll use it

  • Shopping โ€” a “30% off” tag on a $65 item saves $19.50, bringing it to $45.50.
  • Tips โ€” 18% on a $54 bill is $9.72.
  • Grades โ€” 43 correct out of 50 is 86%.
  • Finance โ€” a portfolio moving from $8,000 to $9,000 is an 12.5% gain.

Frequently asked questions

How do I add or remove sales tax?

To add 8% tax to $50, compute 8% of 50 ($4) and add it, giving $54. To find the pre-tax price of a $54 total, divide by 1.08, not subtract 8%.

What is a percentage point vs. a percent?

They’re different. Going from 5% to 7% is a rise of 2 percentage points, but a 40% increase in relative terms. News about rates often confuses the two.

Is my input stored?

No. Every calculation happens in your browser and nothing you type is sent to or saved on our servers.

How it works

For "X% of Y": result = (X/100) ร— Y. For "% change from A to B": result = ((Bโˆ’A)/|A|) ร— 100. For "X is what % of Y": result = (X/Y) ร— 100.

Formula

Portion = (Percentage/100) ร— Total. % Change = ((Newโˆ’Old)/|Old|) ร— 100. % Of = (Part/Whole) ร— 100