What you provide
What you provide
- First numerator a: Non-zero numerator in the first known ratio.
- First denominator b: Non-zero denominator in the first known ratio.
- Second numerator c: Non-zero known numerator paired with the missing denominator x.
ALGEBRA / SOLVE A:B = C:X
Proportion Calculator
Solve the missing fourth term in a proportion using three entered values, with both resulting ratios and the cross-product shown.
- 01 Calculated in this tab
- 02 Values stay in this browser tab
- 03 Use boundary
Use boundary
Calculation path
Cross-products are set equal and the missing denominator is isolated algebraically.
Calculation path
For a / b = c / x, x = b x c / a.
What you receive
What you receive
- Solved fourth term x
- Both ratio values for verification
- Cross-product used in the solution
Use boundary
Choose the maximum decimal places shown. This does not increase source accuracy.
This form solves only a / b = c / x and requires all three known terms to be non-zero so neither displayed denominator becomes zero.
Results are educational math aids. Check notation, units, rounding, assumptions, and required precision before using an answer in graded, engineering, financial, or safety-critical work.