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Free Online Percentage Calculator

Use this free percentage calculator for three everyday jobs: finding a percent of a number (like a tip or tax), finding what percent one amount is of another, or measuring how much a value went up or down in percent.

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How to work with percentages

Percent means “per hundred.” The sign % is a quick way to write a fraction with 100 on the bottom. For example, 25% is the same as 25/100, or 0.25.

Finding a percent of a number: multiply the number by the percent, then divide by 100. If you want 18% of $240, calculate 240 × 18 ÷ 100 = $43.20.

Finding what percent: divide the part by the whole, then multiply by 100. If you scored 42 points out of 50, that's (42 ÷ 50) × 100 = 84%.

Percent increase or decrease: subtract the old value from the new value, divide by the old value, then multiply by 100. A drop from $90 to $72 is a 20% decrease because (72 − 90) ÷ 90 × 100 = −20%.

This tool runs in your browser. Your numbers stay on your device—we do not store them on a server.

Calculating a restaurant tip? Use our tip calculator for bill, tip percent, and split per person.

Worked examples

Real problems you might enter in the calculator above, with short walkthroughs.

  • Restaurant tip: 18% of $85

    85 × (18 ÷ 100) = 15.3. Add that to the bill if you want the total with tip.

    Values18% of 85Answer$15.30

  • Test score as a percent

    (42 ÷ 50) × 100 = 84%. You answered 84% of the questions correctly.

    Values42 of 50Answer84%

  • Sale price went up

    ((156 − 120) ÷ 120) × 100 = 30%. The new price is 30% higher than the original.

    Values120 → 156Answer30% increase

  • Stock dipped

    ((170 − 200) ÷ 200) × 100 = −15%. The value fell by 15% from the starting point.

    Values200 → 170Answer15% decrease

Frequently asked questions about the percentage calculator

  • How do I calculate a percentage of a number?

    Multiply the number by the percentage and divide by 100. Example: 30% of 90 = 90 × 30 ÷ 100 = 27.

  • How do I find what percent one number is of another?

    Divide the smaller part by the total (whole), then multiply by 100. Example: 27 is what percent of 90? (27 ÷ 90) × 100 = 30%.

  • What is the formula for percent change?

    Percent change = ((new value − original value) ÷ original value) × 100. Always use the original value as the base in the denominator.

  • Is this percentage calculator free to use?

    Yes. It is free, works online in your browser, and does not require an account or download.

  • Can I use this for tips, tax, and discounts?

    Yes. Use “percent of a number” for tips and tax. Use “percent change” to see how much a price dropped during a sale.

  • How do I add a percentage to a number (like tax on a price)?

    Find the extra amount with “percent of a number,” then add it to the original. Example: 8% tax on $50 → 50 × 8 ÷ 100 = $4 tax → total $54. Or multiply the price by (100 + rate) ÷ 100: 50 × 108 ÷ 100 = $54.

  • How do I calculate a discount or sale price?

    Use “percent of a number” to get the discount amount, then subtract from the original price. Example: 25% off $80 → discount is $20 → sale price $60. You can also use “percent change” if you know the before and after prices.

  • How do I convert a percentage to a decimal?

    Divide the percent by 100. Examples: 25% = 0.25, 8% = 0.08, 150% = 1.5. To go back, multiply the decimal by 100 (0.45 → 45%).

  • What is the difference between percent increase and percent decrease?

    Both use the same formula: ((new − old) ÷ old) × 100. If the result is positive, the value went up (increase). If negative, it went down (decrease). Our “% change” mode shows this as an increase or decrease label automatically.