Percentage Calculator
Three quick calculators: the percentage of a number, the percent change between two values, and a discounted price.
Percentage of a number
Result
Percent change between two values
Change
Discount price
- Final price
- You save
How is "X% of a number" calculated?
Multiply the number by the percentage and divide by 100 — for example, 15% of 200 is 200 × 15 ÷ 100 = 30.
Why does percent change need a non-zero starting value?
Percent change is (new − old) ÷ old × 100. When the starting value is 0, that division is undefined, so the calculator shows a message instead of a result in that case.
Is anything sent to a server?
No. All three calculators run entirely in your browser with JavaScript — nothing is uploaded or stored anywhere.