Proportion Calculator
Proportion calculator
Solve x in the proportion a / b = c / x.
Result
x = 17.5
Using x = (b × c) / a.
Formula
If a / b = c / x then x = (b x c) / a - Start with proportion a/b = c/x.
- Cross multiply to isolate x.
- Compute x as (b x c) / a.
Example
Worked example: 4/7 = 10/x
- 1 x = (7 x 10) / 4
- 2 x = 70/4
- 3 x = 17.5
The unknown value x is 17.5.
How
- Enter values for a, b, and c.
- Keep a non-zero.
- Read solved x instantly.
Avoid
- Setting a to zero which causes division by zero.
- Swapping b and c during cross multiplication.
- Forgetting that order of terms matters in proportion equations.
Checks
Best fit
Proportion Calculator is built for solve unknown x in a proportion equation using direct cross multiplication. If Proportion Calculator does not match the input scope, compare the answer with a second method.
Input check
Match the entered values to this rule before copying the answer: If a / b = c / x then x = (b x c) / a.
Sanity check
For Proportion Calculator, use the worked example as a quick benchmark: The unknown value x is 17.5. If the proportion calculator answer is far away, check whether an input, unit, or mode changed.
Before copying
Review this common issue first: setting a to zero which causes division by zero.
FAQ
Can I use decimal numbers?
Yes, decimal inputs are supported.
Why does a need to be non-zero?
The solved expression divides by a, so a cannot be zero.
Is this for inverse proportion?
No, this calculator is for direct proportion in the stated equation form.
Switch
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