Percentage Calculator
Calculate percentages, increase/decrease values and change rates.
Percentage Calculation
Percentage Change
What Is a Percentage Calculator and Why Is It Useful?
A percentage calculator helps you find a fraction of a whole, the change between two values, or a part-to-whole ratio. Everyday needs include shopping discounts, salary raise rates, interest returns and exam score percentages.
Three distinct modes let you answer different percentage questions with a single tool: finding a percentage of a number, measuring the ratio between two numbers, or calculating a new value after an increase or decrease.
How to Use
Inputs
Depending on your mode, you enter two numbers. In basic percentage mode: a number and a percentage value. In change mode: an old and a new value. The tool simultaneously calculates ratio, increase and decrease results.
Formulas
Percentage of: Number × Percentage ÷ 100. Finding a percentage: (Part ÷ Whole) × 100. Percentage change: (New − Old) ÷ |Old| × 100. Value after increase: Number × (1 + Percentage ÷ 100). Value after decrease: Number × (1 − Percentage ÷ 100).
Example Scenario
Applying a 20% discount or 20% markup to a product priced at 1,500:
| Operation | Input | Result |
|---|---|---|
| What is Y% of X? | 1,500, 20% | 300 |
| Discounted price | 1,500, 20% decrease | 1,200 |
| Marked-up price | 1,500, 20% increase | 1,800 |
| X as % of Y? | 300 of 1,500 | 20% |
| Percentage change | 1,200 to 1,500 | +25% |
How to Interpret the Results
The percentage amount can be used directly as a discount or surcharge. Increase and decrease values show the new price or quantity directly — no further addition or subtraction needed.
A positive percentage change result means an increase; a negative result means a decrease. When the base value is zero or negative, percentage change becomes mathematically undefined — the tool will show a warning.
Tips for Accurate Results
- 01
In a percentage change calculation, enter the old value in the first field and the new value in the second; swapping them reverses the direction.
- 02
To find a discount rate, don't use the old price as the whole and the new price as the part — use percentage change mode instead.
- 03
For compound percentage applications (e.g. two successive 10% increases), calculate each step separately; the result is not the same as 20%.
- 04
For decimal percentage values (e.g. 8.5%), enter a period as the decimal separator or check your keyboard layout.