Percentage calculator
Two modes. No tax, no compounding - just X% of Y, and A is what % of B.
How to use the Percentage calculator
What does the Percentage calculator do?
Find a percentage of a number, or what percent one number is of another; It applies this page-specific rule: “What is X% of Y” multiplies Y by X/100.
Which inputs does this calculator use?
To find a percentage of a number, or what percent one number is of another, enter Percent, Of, Part, Whole; keep every value in the same example; the page then updates the result from the current values; Start with a familiar case covered by this rule - “A is what percent of B” divides A by B and multiplies by 100 - so the expected result can confirm the settings.
How should the calculator result be read?
For a result intended to find a percentage of a number, or what percent one number is of another, “A is what percent of B” divides A by B and multiplies by 100; read whole together with the original percent rather than as an isolated answer, and confirm that its units or structure match the intended use.
Is this markup vs margin?
When the goal is to find a percentage of a number, or what percent one number is of another, no.
Can I do reverse percentages?
When using the page to find a percentage of a number, or what percent one number is of another, use “part / whole”.
Limits and accuracy
When using this calculator to find a percentage of a number, or what percent one number is of another, this is not markup versus margin, not stacked discounts, and not a tip calculator; check the entered values, units, rounding, and assumptions before using the answer for an important decision; keep percent until the output has been checked in its intended destination. For a repeatable check when you need to find a percentage of a number, or what percent one number is of another, record Percent alongside the final output and selected options.
How this works
“What is X% of Y” multiplies Y by X/100. 17% of 80 is 13.6. That is the usual sale-price or exam-score question.
“A is what percent of B” divides A by B and multiplies by 100. 40 is 20% of 200. If B is 0 the page stops rather than inventing infinity.
This is not markup versus margin, not stacked discounts, and not a tip calculator. Those are different jobs with different formulas.
Frequently asked questions
Is this markup vs margin?
No. Markup is on cost; margin is on sell price. Use the markup vs margin page.
Can I do reverse percentages?
Use “part / whole”. Sale price after 25% off is 75% of the original - that is a different reverse-discount page we have not shipped.
Rounding?
The first result is exact in IEEE floats. The second shows four decimal places.