Ratio Calculator
Calculate ratios and proportions with this free online calculator. Solve for missing values in proportions and scale ratios up or down.
Proportion Calculator (A:B = C:D)
Provide any three values to calculate the fourth in the ratio A:B = C:D.
Ratio Scaling Calculator
Scale a ratio up or down by a specific factor.
About Ratios and Proportions
A ratio is a comparison of two or more numbers that indicates their relative sizes. Ratios are often written with a colon, such as 3:4, which means "3 to 4". A proportion is an equation stating that two ratios are equal.
Understanding Ratios
A ratio compares quantities of the same kind. For example, if a recipe calls for 2 cups of flour and 3 cups of sugar, the ratio of flour to sugar is 2:3.
Ratio of water to cement in concrete: 1:2
Aspect ratio of a widescreen TV: 16:9
Solving Proportions
A proportion is an equation stating that two ratios are equal: A:B = C:D. To solve for a missing value in a proportion, you can use cross multiplication:
Example: If 3:4 = x:20, then 3×20 = 4×x
60 = 4x
x = 15
Scaling Ratios
Scaling a ratio means multiplying or dividing both parts of the ratio by the same number to get an equivalent ratio. This is useful for converting between different units or for scaling recipes.
Scaled up by 5: 10:15
Scaled down by 0.5: 1:1.5
Applications of Ratios
| Field | Application | Example |
|---|---|---|
| Cooking | Recipe scaling | Doubling a recipe that serves 4 to serve 8 |
| Finance | Financial ratios | Debt-to-equity ratio, price-to-earnings ratio |
| Construction | Material mixing | Concrete mix ratio of cement:sand:gravel |
| Art & Design | Proportions | Golden ratio (1:1.618) in design |
| Maps | Scale | Map scale of 1:50,000 |