Percentage Calculator
Six Percentage Problems, One Tool
"Percentage" covers a surprising range of distinct calculations — finding a percentage of a number is a different operation from finding what percentage one number is of another, and both differ again from calculating a tip or a discount. Mixing these up is the most common source of percentage errors. This calculator separates them into six explicit modes so the right formula is always the one being applied.
The Formulas
Percentage of a number: (percent ÷ 100) × number
What percent one value is of another: (value ÷ total) × 100
Percentage increase: ((new − original) ÷ original) × 100
Percentage decrease: ((original − new) ÷ original) × 100
Tip amount: (bill × tip%) ÷ 100
Discount: price − ((price × discount%) ÷ 100)
What percent one value is of another: (value ÷ total) × 100
Percentage increase: ((new − original) ÷ original) × 100
Percentage decrease: ((original − new) ÷ original) × 100
Tip amount: (bill × tip%) ÷ 100
Discount: price − ((price × discount%) ÷ 100)
Where Each Mode Applies
- Percentage of a number — calculating a commission, a sales tax amount, or a portion of a total budget.
- What percent — figuring out test scores, market share, or completion rates.
- Increase / decrease — tracking price changes, salary raises, or year-over-year metrics.
- Tip — splitting a restaurant bill with a target tip percentage.
- Discount — working out a sale price from a percentage markdown.
| Tip % | Tip Amount | Total |
|---|---|---|
| 15% | $9.00 | $69.00 |
| 18% | $10.80 | $70.80 |
| 20% | $12.00 | $72.00 |
| 25% | $15.00 | $75.00 |
Tip amounts calculated as (bill × tip%) ÷ 100, matching the calculator's tip mode exactly.
How to Use This Calculator
- Select the mode you need: Percentage of Number, What Percentage, Percentage Increase, Percentage Decrease, Tip Calculator, or Discount Calculator.
- Fill in the fields that appear for that mode (for example, Original Value and New Value for an increase or decrease).
- Select Calculate to see the result and a plain-language explanation.
Related Calculations
Comparing two values that aren't in a before/after relationship? Use the Percentage Difference Calculator instead, or see Percentage Change for a dedicated increase/decrease tool.