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Percentage Calculator

Solves the three basic percentage questions (a percentage of a number, what percentage one number is of another, and the whole behind a known part and percentage). Always returns the part, the whole and the percent.

When to use

You need a percentage of a value, the percentage one value represents of another, or the base value that a part and its percentage imply.

Do not use when: You need the percentage change between two values (use percentage-change), a price after a percentage discount (use discount) or a tax amount (use sales-tax).

Formula

percent_of: result = x / 100 × y. is_what_percent: result = x / y × 100. percent_of_what: result = x / (y / 100). In every mode part = percent × whole / 100.

Inputs

Parameter	Type	Required	Description
`mode`	enum: percent_of \| is_what_percent \| percent_of_what	default percent_of	Which percentage question to solve; x and y take the meaning shown in the label of the chosen mode.
`x`	number	yes	First number: the percent (percent_of) or the part (is_what_percent, percent_of_what). Percents are plain numbers, 15 means 15%.
`y`	number	yes	Second number: the whole (percent_of, is_what_percent) or the percent (percent_of_what).

Outputs

Output	Type	Unit	Description
`result`	number		The unknown quantity: the part (percent_of), the percent in % (is_what_percent) or the whole (percent_of_what).
`sentence`	string		The solved statement, e.g. '15% of 240 is 36.'
`part`	number		The part: percent × whole / 100.
`whole`	number		The base value that corresponds to 100%.
`percent`	number	%	The percentage: part / whole × 100.

Example

What is 15% of 240?: {"mode":"percent_of","x":15,"y":240} → {"result":36,"part":36,"whole":240,"percent":15,"sentence":"15% of 240 is 36."}

30 is what percent of 120?: {"mode":"is_what_percent","x":30,"y":120} → {"result":25,"part":30,"whole":120,"percent":25,"sentence":"30 is 25% of 120."}

GET https://tttkmbb.com/api/v1/calculate/percentage?mode=percent_of&x=15&y=240

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/percentage (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/percentage · Markdown: https://tttkmbb.com/math/percentage.md · JSON definition: https://tttkmbb.com/math/percentage.json
MCP: server https://tttkmbb.com/mcp, tool calculate_percentage
OpenAPI operationId: calculate_percentage
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Wikipedia – Percentage (reference)
Wolfram MathWorld – Percent (reference)

FAQ

Do I enter 15 or 0.15 for 15%?

Enter 15. Percentages are plain percent numbers everywhere on this site; the calculator divides by 100 internally.

How do I find the whole from a part?

Use mode percent_of_what: '36 is 15% of what?' gives x = 36, y = 15 and returns 240.

What is the difference between percent and percentage points?

Going from 10% to 15% is a rise of 5 percentage points but a 50% relative increase. This calculator handles plain percent arithmetic; use percentage-change for relative changes.

Related calculators

Percentage Change Calculator — Percentage increase or decrease between two values.
Discount Calculator — Price after a percentage discount.
Fraction Simplifier — Express the same part/whole relationship as a reduced fraction.