Percentage Calculator (What % of, % of a number, reverse)
Three basic percentage calculations in one: what percent A is of B, a given percent of a number, and the whole from a part and its percentage. Enter two numbers to instantly get the percent or amount, with your choice of decimal places and rounding.
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Input
Calculation type
Rounding
Round half up
Result
A as a percent of B
15%
30 is 15% of 200.
How it works
- 'What percent is A of B?' divides the compared value A by the base value B and multiplies by 100 (percent = A ÷ B × 100). Example: 30 is 15% of 200.
- 'What is X% of a number?' multiplies the base by the percentage and divides by 100 (amount = base × percent ÷ 100). Example: 15% of 800 is 120.
- 'A is X% of what?' divides the part by the percentage and multiplies by 100 to recover the whole (whole = part ÷ percent × 100). Example: if 120 is 15%, the whole is 800.
- A base value or percentage of 0 cannot be computed (it would divide by zero); check your inputs in that case.
- Results are shown rounded to the number of decimal places you choose, using the selected rounding mode (round half up, round down, or round up).
Frequently asked questions
- How do I find what percent A is of B?
- Divide the compared amount A by the base amount B and multiply by 100 (percentage = A ÷ B × 100). For example, 30 is 15% of 200.
- What is the difference between finding a percent of a total and working the total back out?
- To get a percent of a total, use total × percent ÷ 100 (15% of 800 is 120). To reverse it, divide the part by the percent and multiply by 100 (if 120 is 15%, the total is 800).
- Can it round results and handle edge cases?
- Yes. You can choose the number of decimal places and the rounding mode (round, floor, or ceiling). Note that it cannot compute when the base amount or the percentage is zero, since that would divide by zero.
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