Ratio Calculator

Solve proportions, simplify ratios, and find missing values in ratio equations. Free online ratio and proportion calculator.

Frequently Asked Questions

How do I solve for a missing value in a proportion?
In a:b = c:x, the missing value x = b x c / a. Enter the three known values and the calculator finds the fourth automatically.
Can ratios be simplified to lowest terms?
Yes, the calculator divides all parts of the ratio by their greatest common divisor to produce the simplest integer ratio. For example, 12:8 becomes 3:2.
Can I work with ratios of three or more numbers?
Yes, you can simplify and scale ratios with three or more terms, such as a:b:c.
Verified 2026 formulas