Percentage Calculator

How to use Percentage Calculator

1. Pick the calculation you need from the three cards.
2. Enter your two numbers.
3. The answer updates instantly.

The three core formulas

• Part of a whole: Y × (X ÷ 100). Example: 20% of 150 = 30.
• Percent one number is of another: (X ÷ Y) × 100. Example: 30 is 25% of 120.
• Percentage change: (New − Old) ÷ |Old| × 100.

Everyday examples

Shopping: a jacket costs 80 with 25% off, so the discount is 80 × 0.25 = 20 and you pay 60. Tips: 15% of a 46 bill is 6.90. Exam marks: 42 out of 60 is 70%. Salary: a rise from 30,000 to 32,400 is an 8% increase.

Percent vs percentage points

If an interest rate rises from 4% to 5%, it increased by one percentage point, but by 25% in relative terms. News reports often mix these up, so check which is meant. Percentage change from zero is undefined, which is why the calculator shows a dash when the starting value is 0.

Mental-maths shortcuts

To find 10% of any number, move the decimal point one place left. Then 20% is double that, 5% is half, and 15% is 10% plus 5%. For 1% move two places. These shortcuts handle most tips, discounts and tax estimates without a calculator.

To reverse a percentage change, remember that the base changes. If a price rises 25%, you need a 20% cut to come back down, not 25%. The same logic explains why losing 50% of an investment requires a 100% gain to recover.

Why use this percentage calculator tool

• Three calculators. Percent of, percent is, and percent change.
• Instant. Answers update as you type.
• Clear formulas. The guide below explains each one.

Frequently asked questions

More free tools