Proportion Calculator
Free online proportion calculator that runs entirely in your browser.
How the Proportion Calculator works
The Proportion Calculator works on A, B, C and shows the result as you type. The same input always gives the same answer — refresh the page and you will see exactly the same figure.
Formula used
Proportion Calculator is computed by the formula below, using the inputs you provide.
Inputs used: A, B, C.
Worked example
Take the default example — a of 3, b of 4, c of 15:
- D (the missing value): 20
- relation: A:B = C:D → 3:4 = 15:20
Frequently asked questions
- Is the Proportion Calculator free?
- Yes. There is no signup, no usage limit and no watermark — the calculator runs entirely in your browser.
- Does the Proportion Calculator store or send my data?
- No. Every calculation happens locally in the page, so the numbers you type are never uploaded or logged.
- Does it work on a phone and offline?
- Yes — the page is a single lightweight file that adapts to any screen size. Once it has loaded it keeps working without a network connection.
- What inputs does the Proportion Calculator need?
- A, B, C. Change any of them and the result updates instantly.