Utilities

Percentage Calculator

Calculate percentages, find percentage changes, and increase or decrease numbers instantly with our free online percentage calculator.

Choose a calculation

Select a question, enter the values, and see the result update as you type.

Calculation type

Your result

Enter the values above to calculate instantly.

Common percentage calculations

  • Discount: 15% of $80 is $12.
  • Change: 100 to 125 is a 25% increase.
  • Adjustment: Decrease 200 by 15% to get 170.

How percentages work

A percentage is a number out of 100. To find a percentage of a number, divide the percentage by 100 and multiply by the number. For example, 20% of 150 is (20 ÷ 100) × 150 = 30.

Find what percentage one number is of another

Divide the part by the total and multiply by 100. For example, 45 ÷ 150 × 100 = 30%, so 45 is 30% of 150. A zero total has no defined percentage result.

Calculate percentage change

Subtract the original value from the new value, divide by the absolute value of the original, then multiply by 100. This uses the original value's magnitude as the reference, so a result above zero is an increase and one below zero is a decrease. For example, 100 to 125 is +25%; 100 to 75 is −25%. When the original is zero, percentage change is undefined.

Increase or decrease a value

For an increase, multiply the starting value by (1 + percentage ÷ 100). For a decrease, multiply it by (1 − percentage ÷ 100). Increasing 200 by 15% gives 230; decreasing 200 by 15% gives 170. A decrease greater than 100% can produce a negative result.

Using the Percentage Calculator

  1. 1Choose one of the four calculation questions.
  2. 2Enter the requested values. The result and explanation update immediately.
  3. 3Copy the result if needed, or use Clear to reset the inputs without reloading.

Help and limitations

  • A zero total cannot be used as a percentage denominator, and percentage change from an original value of zero is undefined.
  • The increase/decrease mode accepts only a nonnegative percentage; a decrease above 100% may produce a negative result.
  • JavaScript numbers use normal binary floating-point precision. Display formatting reduces common representation artifacts, but this calculator is not intended for high-precision financial accounting.

Frequently asked questions

How do I find a discount amount?
Choose Percentage of a number and enter the discount rate and original price. For example, 15% of 80 is 12. Subtract that amount from the price if you want the price after discount.
Why is percentage change undefined from zero?
The percentage-change formula divides by the magnitude of the original value. If the original is zero, there is no reference magnitude for the calculation.
Are these results suitable for accounting?
No. This tool uses JavaScript's standard floating-point numbers and is intended for everyday estimates, not high-precision financial or accounting work.

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