Ratio Calculator

Simplify a ratio, or solve a proportion by leaving one value blank.

Simplify: fill A and B. Solve a proportion: fill three of the four boxes, leave one blank.

:
=
:

Frequently asked questions

How do I simplify a ratio?

Enter the two values in A and B. The calculator divides both by their greatest common divisor to give the simplest whole-number ratio, plus the decimal (X : 1) form.

How do I solve a proportion?

Write it as A:B = C:D and leave the unknown box blank. With three values filled, the tool solves the fourth using cross-multiplication.

What can I use ratios for?

Scaling recipes, mixing paint or fuel, aspect ratios, map scales and any situation where two quantities keep a fixed proportion.