Proportion Calculator
Solve a/b = c/d when exactly one value is unknown.
Proportion
Solve a/b = c/d when one value is unknown.
Fill in three values and leave one blank to solve for it.
/=/
Solving for d
15
How it works
Enter three of the four terms a, b, c, d and leave exactly one blank to solve for it.
The proportion a/b = c/d is cross-multiplied and rearranged to solve for the missing term.
Exactly one of a, b, c, d should be left blank — that is the term this calculator solves for.
Formula
a / b = c / d
Worked example: 2/5 = 6/15