Ratio Calculator
Enter three values — leave one blank to solve for it.
Enter a ratio to simplify to its lowest terms.
Scale a ratio by a multiplier.
Result
—
Solving a Proportion
Common Uses
- Scaling recipes: If a recipe for 4 serves uses 2 cups of flour, how much for 6 serves? → 2:4 = X:6 → X = 3 cups
- Map distances: If 1 cm = 50 km, how far is 3.5 cm? → 1:50 = 3.5:X → 175 km
- Mixing: A paint mix is 3 parts red to 2 parts white. To make 25 liters total: 3:2 scaled × 5 = 15L red + 10L white
Frequently Asked Questions
What is a ratio?
A ratio expresses the relationship between two or more quantities. The ratio 3:2 means for every 3 of one thing, there are 2 of another. Ratios can be written as A:B, A/B, or "A to B." They are used in recipes, maps, finance, and everyday comparisons.
What is a proportion?
A proportion is an equation stating that two ratios are equal: A/B = C/D. Cross-multiplying gives A × D = B × C, which allows you to solve for any missing value. Proportions are used in scaling, currency conversion, unit conversion, and many other practical calculations.
How do I simplify a ratio?
Divide both numbers by their greatest common factor (GCF). For example, 12:8 → GCF is 4 → 3:2. A simplified ratio is equivalent to the original but expressed in the smallest whole numbers.
What is aspect ratio?
Aspect ratio is a specific ratio describing the proportional relationship between width and height — common in screens, images, and video. 16:9 is the standard widescreen ratio. 4:3 was the old TV standard. A 1920×1080 pixel image has a 16:9 aspect ratio (1920/1080 simplifies to 16/9).