Business Finance
Percentage Calculator
Calculate a percentage of a number, find what percent one number is of another, or work backward to the original whole. Choose your question to see the answer and its calculation.
Your result
Ready when you areTurn a percentage into an amount.
Choose a task and enter your numbers. You’ll get an answer with the arithmetic behind it.
The method
Three questions, one percentage relationship
A percentage expresses a ratio per hundred. To find a part, divide the percentage by 100 and multiply by the base. To find the percentage, divide the part by the whole and multiply by 100. To recover a whole, divide the known part by the percentage and multiply by 100. Keep both amounts in the same unit. This calculator uses exact decimal arithmetic before rounding the displayed answer to at most six decimal places.
Example 1
Find 15% of 240
Divide 15 by 100 to get 0.15, then multiply by 240. The result is 36. If these numbers describe a discount, 36 is the amount taken off; the remaining price would be 204.
- Percentage
- 15%
- Base
- 240
- Part
- 36
Example 2
Find the rate or recover the whole
The same values work in reverse: 36 ÷ 240 × 100 = 15%, while 36 ÷ 15 × 100 = 240. For a repeating result, 1 is approximately 33.333333% of 3; that display is rounded, not an exact terminating decimal.
- Part
- 36
- Whole
- 240
- Percentage
- 15%
Example 3
A percentage can be greater than 100
125% of 80 is 100. For a positive base, a percentage above 100 means the part is larger than the comparison base; it is valid arithmetic. The appropriate limit for a real-world metric still depends on what that metric counts.
- Percentage
- 125%
- Base
- 80
- Part
- 100
Before you calculate
Assumptions & limits
- Use numbers in the same unit. This is a general percentage calculation, not a tax, profit, growth-rate or currency conversion model.
- Inputs may be positive, zero or negative, with up to six decimal places and absolute value no greater than 1,000,000,000,000. Use a decimal point without grouping commas, a percent sign or scientific notation.
- The whole in rate mode and the percentage in find-whole mode must be nonzero. A 0% part does not uniquely identify its whole. Zero percentage and zero base are valid when finding a percentage of a number.
- Outputs support magnitude up to 1,000,000,000,000,000,000. Display rounding is to six decimals, halfway away from zero; tiny nonzero results are shown as a bound rather than an exact zero.
- Negative inputs follow signed algebra. They do not select a convention for percentage change from a negative starting value. Entered numbers and results are not saved or put in URLs or analytics.
Keep in mind
Common mix-ups
Percentage change uses the starting value
Moving from 80 to 100 is a 25% increase: (100 − 80) ÷ 80 × 100. Returning from 100 to 80 is a 20% decrease because the starting base changes. Conventional relative change from zero is undefined; negative bases require a stated convention. Change is a separate comparison from the three part-and-whole tasks above.
Percentage points are not relative percent change
A rate going from 20% to 25% rises by five percentage points. Relative to the original 20%, that is a 25% increase. Always say which comparison you mean.
Percentage difference is another comparison
For two positive measurements without a starting baseline, a common percentage-difference formula divides their absolute gap by their mean. For 80 and 100, that gives about 22.222222%. It is not the 25% directional change or the 20% reverse change, and is not an extra mode in this tool.
Sources & calculation notes
Explains the amount, base and percentage relationship. Worked examples, exact decimal handling and input bounds here are BiznTools calculations.
Reference for the three part, percentage and whole equations. It is an independent calculator, not an endorsement of BiznTools.
Calculation and input rules checked: . Engineering validation; no professional accounting review is claimed.