Ratio Calculator

The Ratio Calculator has two modes: Simplify a ratio to its lowest terms, or solve a proportion to find a missing value (A:B = C:?).

A ratio expresses the relative sizes of two quantities. The ratio 6:9 and 2:3 represent the same relationship — one is just scaled up by 3. Ratios appear everywhere: cooking (2 cups flour to 1 cup water), maps (1:50,000), probability, and finance.

Simplifying a ratio works exactly like simplifying a fraction: divide both parts by their Greatest Common Factor (GCF). For 6:9, GCF(6,9) = 3, so 6:9 simplifies to 2:3.

Solving a proportion (A:B = C:D) uses cross-multiplication: D = (B × C) / A. This is essential for scaling recipes, converting units, reading maps, or solving similar-triangle problems in geometry.

Example

Simplify 24:36.

GCF(24, 36) = 12. So 24:36 = 2:3.

Proportion: If 2:3 = 8:?, find the missing value.

Using D = B × C / A: D = 3 × 8 / 2 = 12.

So 2:3 = 8:12. Both ratios simplify to 2:3, confirming the answer is correct.

Real-world use: if a recipe calls for 2 cups of flour for every 3 cups of liquid, and you're scaling up to 8 cups of flour — you need 12 cups of liquid.