Ratio Calculator
The ratio calculator simplifies ratios, finds missing values in proportions using cross-multiplication, and scales ratios. Enter two values in a ratio to simplify it, or use proportion mode to solve for an unknown value in A:B = C:D proportions.
Ratio simplification
| Ratio | Simplified |
|---|---|
| 2:4 | 1:2 |
| 6:9 | 2:3 |
| 10:15 | 2:3 |
| 12:8 | 3:2 |
| 15:25 | 3:5 |
Ratio calculator: frequently asked questions
What is a ratio?
A ratio is a comparison of two quantities. For example, a recipe might call for 2 cups of flour to 1 cup of sugar, expressed as the ratio 2:1. Ratios can be simplified like fractions.
How do I simplify a ratio?
Divide both parts by their greatest common divisor (GCD). For example, 6:9 has GCD(6,9) = 3, so it simplifies to 2:3.
What is a proportion?
A proportion is an equation stating that two ratios are equal. For example, 2:3 = 4:6. If you know three values in A:B = C:D, you can find the fourth using cross-multiplication: D = B*C/A.
How do I scale a ratio?
Multiply both parts by the same factor. For example, 2:3 scaled by 5 becomes 10:15.
When do I use ratios?
Ratios are used in cooking, mixing, scaling drawings, comparing quantities, and probability. They appear in maps, recipes, and recipes.
Official sources
- Standard mathematical formula for ratio simplification and proportions.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.