Proportion Calculator
Given a:b = c:x, compute x = (b × c) ÷ a.
Calculator
Use the Proportion Calculator
Result
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Formula
x = (B × C) ÷ A
Step-by-step
- 1
Enter A, B, C
Provide the known ratio a:b and the value c.
- 2
Compute x
Calculate x using x = (B × C) ÷ A.
Worked example
Example input: a: 2, b: 3, c: 4
Result: 6
Related tools
- Ratio Calculator
Compute decimal ratio A ÷ B.
Frequently asked questions
What does the proportion calculator solve?
The missing fourth term of a cross condition: knowing a : b = c : d it returns d = (b x c) / a. The example 2 : 3 = 4 : ? gives (3 x 4) / 2 = 6, matching the answer shown above.
How is a proportion different from a ratio?
A ratio compresses two numbers into one decimal like 2 : 3 equals about 0.67; a proportion takes two known pairs and finds the unknown partner. The ratio tool is the one-number view, this page is the find-the-missing-term view.
Why must the first term be nonzero?
A proportion with a on zero has no meaningful cross product to solve through — the relation collapses. The tool reports no usable answer for that input rather than a made-up number.