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Quick guide

What This Calculator Does

This ratio calculator combines three common tasks: reducing an integer ratio to lowest terms, generating an equivalent ratio at a chosen scale, and solving one missing term in a : b = c : d. The result also shows a greatest common divisor, decimal and percentage views, quick multiples, or cross products, so you can check the work instead of receiving one isolated number.

It is useful for classroom practice, scaling and mixture problems, recipes, map or model scales, and straightforward numerical checks. For arithmetic with fractions, use the fraction calculator. If you only need the greatest common divisor of two integers, use the GCF calculator.

When to Use It

  • You want to reduce 12 : 18 to lowest terms.
  • You want to scale a ratio, such as expanding 2 : 3 by a factor of 4.
  • You want to solve a proportion such as 4 : 7 = x : 21.
  • You want to see the decimal and percentage interpretation of a ratio.
  • You want to verify a solved proportion with cross products.

Inputs Explained

Modes

The page provides three modes:

  • Simplify Ratio finds the greatest common divisor and returns the lowest-term ratio.
  • Equivalent Ratio simplifies the ratio, applies a positive integer scale factor, and lists the ×1 through ×5 multiples.
  • Solve Proportion leaves one position blank in a : b = c : d and solves for it.

Simplify and Equivalent Modes

Read the full guide

Frequently Asked Questions

Which modes does this page support?

It supports ratio simplification, equivalent-ratio scaling, and proportion solving.

Can simplify and equivalent modes use decimals?

No. Those modes require integer terms; proportion mode accepts ordinary numeric values.

What is required in proportion mode?

Leave exactly one of a, b, c, or d blank, enter valid values in the other three fields, and the page solves it by cross multiplication.

Can a ratio term be zero?

The second term cannot be zero in simplify or equivalent mode, and completed proportion values b and d cannot be zero.

Does it calculate automatically?

Yes. Once the current mode has enough valid input, the result updates automatically, and the Calculate button runs the same logic manually.

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Ratio Calculator

Simplify integer ratios, scale equivalent ratios, and solve one missing term with ordinary numeric values in a proportion.

Ratio Tools

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Use whole numbers for ratio simplification and equivalent ratio generation.