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Ratio Calculator Tool

Simplify ratios to their lowest integer terms, or solve the missing term in an A:B = C:? proportion. Works with both integers and decimals.

Last updated: 2026/10/16 Calculator Feedback & bug reports
Simplify a Ratio

Divide the ratio by its greatest common divisor to get the simplest integer ratio.

: = ?
e.g. 1920 : 1080 -> 16 : 9
Solve a Proportion (A:B = C:?)

Find the missing term from the proportion A : B = C : ?.

: = : ?
e.g. 2 : 3 = 10 : ? -> 15

How to Use

1

Choose a Mode

Pick "Simplify a Ratio" or "Solve a Proportion" depending on your goal.

2

Enter Values

Type numbers into the fields and results appear instantly.

3

Copy the Result

Use the copy button next to the result to copy it.

About Ratio Calculation

A ratio such as "A : B" expresses the relationship between two or more quantities. Reducing a ratio to its simplest integer form makes aspect ratios, recipe amounts, and map scales easier to understand. A proportion of the form "A : B = C : ?" lets you find a corresponding value from a known ratio. This tool runs entirely in your browser, so the numbers you enter are never sent to a server.

Features

  • Ratio ReductionDivides by the GCD to give the simplest integer ratio.
  • Proportion SolverFinds the missing term in A:B = C:? automatically.
  • Integers & DecimalsDecimal ratios are converted to integers for accurate results.
  • Real-time CalculationResults appear instantly as you type. No buttons needed.

Use Cases

  • Check screen/image aspect ratios (like 16:9)
  • Scale recipe amounts to different servings
  • Calculate map and blueprint scales
  • Mixing and dilution ratios for paint or chemicals
  • Currency and unit conversion proportions

FAQ

Is the ratio calculator free to use?
Yes, it is completely free. No registration or installation is required - just open it in your browser and start using it.
Can it handle ratios with decimals?
Yes. For example, entering 1.5 : 2.5 reduces to 3 : 5. Decimals are converted to integers internally before reducing by the greatest common divisor.
What does "simplify a ratio" mean?
It means dividing each term by their greatest common divisor (GCD) to get the simplest integer ratio. For example, 1920 : 1080 divides by 120 to become 16 : 9.
How is A:B = C:? solved?
In the proportion A : B = C : ?, the missing term is ? = B x C / A. For example, 2 : 3 = 10 : ? gives ? = 3 x 10 / 2 = 15.
Are the numbers I enter sent to a server?
No. All calculations run entirely in your browser using JavaScript, and the numbers you enter are never sent to or stored on any external server.

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