ToolNova

➗ Percentage Calculator — multi-purpose percentage tools

An all-in-one percentage calculator. Instantly find X% of Y, calculate what percentage one number is of another, determine percentage change from one value to another, or solve reverse percentages.

Math Free · no sign-up Added 2026-08-05
Input
Result

Private by design. This tool runs entirely in your browser — nothing you enter or add is uploaded to any server.

How it works

  1. Enter values in any of the four sections — each calculator works independently and updates instantly.
  2. Section 1 calculates the final value when a percentage is applied to a base number.
  3. Section 2 calculates the ratio between two numbers and displays it as a percentage.
  4. Section 3 determines the relative difference between a starting value and an ending value, showing the percent increase or decrease.
  5. Section 4 performs a reverse percentage calculation to find the original base amount.

Examples

  • 15% of 200 is 30.
  • 50 is 25% of 200.
  • The percentage change from 100 to 150 is a 50% increase.
  • If 40 is 20% of a number, the original number is 200.

Frequently asked questions

How is a percentage calculated?

A percentage is a fraction of 100. To find the percentage of a number, divide the percentage by 100 and multiply by the number: (percentage / 100) * value.

How do you calculate percentage increase or decrease?

Find the difference between the new value and the old value, divide that difference by the old value, and multiply by 100: ((new - old) / old) * 100. A positive result is an increase, and a negative result is a decrease.

What is a reverse percentage?

A reverse percentage finds the original number when only a portion (the percentage amount) is known. It is calculated by dividing the value by the decimal percentage: value / (percentage / 100).

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