Ratio Calculator
Simplify a ratio or solve A : B = C : D for the missing value.
How this calculator works
The ratio A : B is simplified by dividing both numbers by their greatest common divisor. To solve A : B = C : D, the missing value is D = B x C / A.
Frequently asked questions
How do I simplify a ratio?
Divide both parts by their greatest common divisor. For example, 6 : 8 becomes 3 : 4.
Can I use decimals?
Yes. The calculator scales decimals to whole numbers before simplifying.
How do I find a missing value in a proportion?
Enter A, B and C. The missing D keeps the same ratio as A : B.
