Proportion Calculator
Free, instant proportion calculator with step-by-step solutions, transparent formulas, and verification.
Quick answer
A proportion sets two ratios equal. Enter three known values to solve the missing value, or switch to Verify to test whether a/b and c/d are equivalent.
Formula and calculation method
a/b = c/d → a × d = b × c. For d, d = (b × c) / a.
Use the interactive Toolune page
Enter your values in the browser tool to see the result, worked steps, assumptions, and related learning guides.