Ratio Calculator

Modify the values and click the Calculate button to use

A : B = C : 800

Solved value: X = 800
Simplified ratio: 3 : 4
Decimal ratio: 0.75

A proportion states that two ratios are equal. Cross-multiply to solve: A × X = B × C, so X = B × C ÷ A.

What this ratio calculator does

A ratio compares two quantities. This calculator solves the proportion A : B = C : X for the missing value X and simplifies the ratio A : B.

Ratios are used in recipes, maps, scale models, mixtures, and financial comparisons.

How to use this calculator

Enter A, B, and C.
Click Calculate to find X.
The simplified ratio and decimal ratio are shown below the result.

The default example is 3 : 4 = 600 : X.

Ratio formulas

A : B = C : X
A × X = B × C
X = B × C ÷ A

To simplify A : B, divide both sides by their greatest common divisor.

What the results mean

For the default example, X = 800, so 3 : 4 = 600 : 800. The simplified ratio is 3 : 4, and the decimal ratio is 0.75.

A ratio does not imply a total. If a recipe uses a 3 : 4 ratio and the total is 700, the parts are 300 and 400, but the calculator solves the proportion you enter rather than splitting a total.

Assumptions and limitations

A cannot be zero because the formula divides by it. B and C can be negative, but the result is a proportional solution, not a physical quantity. The calculator does not enforce units.

It simplifies integer ratios; decimals and fractions may produce a decimal result.

Frequently asked questions

How do I solve a proportion?

Cross-multiply: A × X = B × C, then divide by A. The calculator does this automatically.

What does a 3 : 4 ratio mean?

For every 3 units of the first quantity, there are 4 units of the second. The decimal ratio is 0.75.

Can ratios have decimals?

Yes. A ratio can compare any two numbers, including decimals. The calculator shows the decimal value of A ÷ B.

Is a ratio the same as a fraction?

A ratio compares two quantities and can be written as a fraction. A fraction usually represents a part of a whole; a ratio can compare parts to parts or parts to a whole.

Reference table

Common aspect ratios

Name	Aspect ratio	Width (pixel)	Height (pixel)
SD video	4:3	640	480
HD video	16:9	1920	1080
4K UHD	16:9	3840	2160
Cinema wide	21:9	2560	1080
Square	1:1	1080	1080
Portrait	9:16	1080	1920

Source

Reference: Wolfram MathWorld — Ratio.

Disclaimer

This calculator is for educational purposes. Confirm units and context for real-world applications.

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