Ratio Calculator
Free online ratio calculator. Solve for missing values in A:B = C:D proportions, simplify ratios, and find equivalent ratios instantly.
A ratio expresses the relative size of two or more quantities. This calculator can solve for a missing value in a proportion A:B = C:D, simplify a ratio to its lowest terms, and generate a list of equivalent ratios. Ratios are used everywhere from recipes and maps to financial analysis.
Solving Proportions
- Cross multiplication: If A:B = C:D, then A×D = B×C (cross products are equal)
- Example: 2:3 = 8:? → ? = 3×8/2 = 12
- Scale models: If 1 cm = 50 km on a map, what does 3.5 cm represent? → 175 km
Simplifying Ratios
To simplify a ratio, divide both terms by their Greatest Common Divisor (GCD). For example, 12:18 has GCD = 6, so 12:18 = 2:3. In cooking, a recipe ratio of 250 ml:375 ml simplifies to 2:3. Keeping ratios in simplest form makes comparisons and scaling much easier.