Ratio Calculator

Simplify a ratio, or find the missing value in a proportion.

Result

Enter values and press Calculate to see the result.

Formula

a:b=c:x  ⇒  x=bcaa : b = c : x \;\Rightarrow\; x = \frac{b c}{a}

In a proportion the cross products are equal: a·x = b·c.

How to use this calculator

  1. Choose simplify or proportion, then enter positive numbers.
  2. Decimals and fractions are fine: 1.5 : 2 simplifies to 3 : 4.

Worked example

Simplify 12 : 18

The greatest common divisor of 12 and 18 is 6.

12 : 18 = 2 : 3, which is 1 : 1.5 as a unit ratio.

Frequently asked questions

What is a unit ratio?

The same ratio scaled so the first term is 1, which makes comparisons easy.

How do I scale a recipe?

Use proportion mode: if 4 servings need 200 g, then 4 : 200 = 6 : x gives the amount for 6.

Learn more