Percentage
Calculate percentages, increases, discounts, and proportions.
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Tool guide
Percentage: how it works
Practical information to understand the result and use this tool correctly.
About Percentage
Percentage problems show up in discounts, tips, taxes, grades, and growth rates. This calculator handles common cases: finding a percent of a number, finding what percent one number is of another, and percent change.
All math runs locally so you can check store prices, markups, or homework without a spreadsheet.
Percent change is (new − old) / old. Be careful with the base: “20% off” applies to the original price, not to a price that was already discounted unless the offer says so.
How to use it
- 1Pick the mode you need (percent of, reverse percent, or change).
- 2Enter the numbers involved.
- 3Read the result and units (amount vs percentage points).
- 4Double-check the base amount for discounts and increases.
Frequently asked questions
- How do I calculate a discount?
- Multiply the original price by (1 − discount%). Example: $80 with 25% off → 80 × 0.75 = $60.
- Percent vs percentage points?
- If a rate goes from 10% to 12%, that is a rise of 2 percentage points, or a 20% relative increase.