Ratios and proportions

Simplify a ratio or solve the missing side of a proportion.

Switch between two focused modes so the relationship and formula stay explicit.

Result—

Enter values and calculate to see the formula here.

Ready.

How the modes work

Simplifying uses the greatest common divisor.

For example, 84:126 divides both values by 42 to produce 2:3.

For a:b = c:x, the missing value is x = (b × c) ÷ a. The first value a cannot be zero.

Can a simplified ratio include a negative value?

Yes. The sign is normalized so the second value is non-negative.

Does the proportion solver require whole numbers?

No. The proportion mode accepts finite decimal values; simplify mode uses whole numbers so greatest-common-divisor reduction is exact.

Keep checking

Add, subtract, multiply, and divide exact fractions with automatic reduction and mixed-number output when useful.

Calculate percent-of, percent ratio, and percentage increase or decrease with the working formula shown.

Calculate area and perimeter or circumference for rectangles, circles, and valid triangles with formulas shown.