What is a Ratio?

A ratio is a mathematical relationship between two or more numbers that shows how many times one value contains another. Ratios are commonly written using a colon symbol ( : ), such as 2:1, or expressed as a fraction like 2/1.

For example:

2 : 1

means the first value is twice as large as the second value.

Ratios are used widely in mathematics, science, finance, cooking, and everyday comparisons. They help describe proportions, scaling, and relationships between quantities.

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Ratio Formula

A ratio comparison is often written as:

A : B = C : D

To find the missing value, we use cross multiplication:

A × D = B × C

Example:

3 : 4 = 600 : D

Solve for D:

3 × D = 4 × 600
3D = 2400
D = 800

So the complete ratio becomes:

3 : 4 = 600 : 800

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Example of Ratio Calculation

Suppose a recipe requires ingredients in the ratio:

Butter : Sugar : Flour = 1 : 2 : 3

If you want to make 5 times the recipe, multiply each value by 5:

5 : 10 : 15

This scaling keeps the same ratio between ingredients.

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Common Uses of Ratios

Ratios appear in many everyday situations, such as:

Cooking recipes
Financial comparisons
Map scale
Screen aspect ratios
Probability and statistics

For example, a screen aspect ratio describes the relationship between width and height.

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Common Screen Aspect Ratios

Resolution	Aspect Ratio	Width	Height
720p	16:9	1280	720
1080p	16:9	1920	1080
4K UHD	16:9	3840	2160
SVGA	4:3	800	600
XGA	4:3	1024	768
WQHD	16:9	2560	1440

Aspect ratios are important for video resolution, screen displays, and image scaling.