Rule of Three Calculator — Find X from Three Values
CalculatorA rule of three calculator finds the unknown X in A:B = C:X from the three known values A, B, and C.
What is it
A proportion states that two ratios are equal. If A corresponds to B and C corresponds to X, then X is calculated by multiplying B and C and dividing by A.
X = B × C / A
How to use
- 1Enter the base values A and B.
- 2Enter the comparison value C.
- 3Press calculate to find X.
Reference
| A | B | C | X |
|---|---|---|---|
| 4 | 10 | 6 | 15 |
| 3 | 12 | 5 | 20 |
Sources & standards
- MDN Web Docs: Client-side web APIs - MDN Web Docs
FAQ
How do I find X in A:B = C:X?
Use X = B×C/A. For example, if 4:10 = 6:X, then X = 10×6/4 = 15.
Is rule of three calculator input sent to a server?
No. This tool runs in your browser and does not send input to a server.