Runs locally in your browser

Ratio Calculator

Simplify a ratio to lowest terms or solve a missing value in A:B = C:D. Proportion math runs locally in this browser tab.

Left

Right

Simplified: 2:3

Missing d: 15.0000

Use this when a recipe, a map scale, or a mix needs A to B in lowest terms, or when three of four proportion slots are known.

Greatest common divisor and cross-multiply run in the browser. Nothing is posted to a solver.

How to use

Simplify divides both sides by their greatest common divisor. Solve fills C as A times D over B, or D as B times C over A.

Leave exactly one of C or D empty. Dividing by zero returns an error. This is not a list mean.

Recipe scale
8:12 flour to water simplifies to 2:3. Triple a 2:3 mix by solving the missing large side.
Map legend
1:50000 with 3 cm on the map solves the ground distance on the other side of the proportion.

Can both C and D be empty?

No. Leave exactly one of those two blank so the solver knows which side to fill.

Do decimals work?

Yes. The gcd path uses integers when possible. Cross-multiply works with decimals too.

Is this a percentage?

A ratio 1:4 is not the same as 25 percent unless you convert it. Use the percentage tool for percent questions.

Does solving happen on a server?

No. Proportion math is client-side.