Ratio Calculator

How equivalent ratios work

Two ratios are equivalent when their cross products match: A : B = C : D means A × D = B × C. To solve 2 : 3 = x : 12, multiply 2 × 12 = 24 and divide by 3, giving x = 8.

Simplifying a ratio

Dividing both sides by their greatest common divisor gives the simplest form. For example 8 : 12 simplifies to 2 : 3, and 1920 : 1080 simplifies to 16 : 9.

Everyday uses

• Recipes: scaling ingredients from 2 servings to 5.
• Screens and images: keeping the 16:9 or 4:3 aspect ratio when resizing.
• Maps and models: converting between scale drawings and real distances.