Proportion Calculator
Solve a simple proportion in the form a/b = c/x.
Results are provided for general informational use. Verify important financial, health or legal figures before relying on them.
About this Proportion Calculator
The Proportion Calculator solves a common cross-multiplication problem where three values are known and the fourth is unknown. It can help with scale drawings, recipes, rates, conversions and classroom proportion exercises.
For related tasks, try Ratio Calculator, Fraction Calculator or Percentage Calculator.
How the calculation works
From a/b = c/x, cross multiplication gives a × x = b × c. The calculator therefore solves x = (b × c) ÷ a when a is non-zero.
How to use it
- Enter values for a, b and c.
- The tool treats the equation as a/b = c/x.
- Calculate to solve for x.
Practical example
If 2/5 = 6/x, cross multiplication gives x = 15.
Frequently asked questions
Can I solve for a different position?
This version solves for x in a/b = c/x. Rearrange your values to match that form.
Can decimals be used?
Yes. Integer and decimal values are supported.
What if a is zero?
The calculator cannot divide by zero, so a must be non-zero.
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