Percentage Calculator

A percentage calculator solves common percent problems. This tool finds X% of a number, what percent one number is of another, the percentage change between two values, a value after an increase or discount, the original number from a percentage, and the percentage difference. It shows the formula it used and updates as you type.

Free, no signup. Runs entirely in your browser; files and text are not uploaded.

How to use the Percentage Calculator

  1. Choose a Calculation, such as “What is X% of Y?”.
  2. Enter the two values in the labelled boxes.
  3. Read the result sentence and the formula used.
  4. Press Copy to copy the result.

Features

  • Seven calculations: percent of, what percent, percentage change, increase, decrease/discount, reverse percentage and percentage difference
  • Shows the formula with your numbers
  • Shows the amount added, saved or changed where relevant
  • Handles negative numbers and warns about division by zero
  • Accepts numbers with thousands separators
  • Remembers values separately for each calculation

Frequently asked questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. For example, 20% of 150 is 0.20 × 150 = 30.

How do I calculate percentage change?

Subtract the old value from the new value, divide by the old value and multiply by 100. From 80 to 100 is (100 − 80) ÷ 80 × 100 = 25% increase.

How do I work out the original price before a discount?

Use “X is P% of what number?”. If a sale price of 45 is 75% of the original, the original is 45 ÷ 0.75 = 60.

What is the difference between percentage change and percentage difference?

Percentage change compares a new value with an old one. Percentage difference compares two values with no order, dividing by their average.

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Built and reviewed by Naqash Thaheem, Technical Project Manager. Last reviewed 2026-09-24.