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Ratio Calculator

Simplify a ratio, and solve for a missing value in a proportion.

Simplify a Ratio
Solve a Proportion (A:B = C:?)

Enter your numbers and select Calculate to see results.

About This Calculator

This calculator simplifies a ratio (A:B) to its lowest terms, and separately solves for a missing fourth value in a proportion (A:B = C:?) — useful for recipes, scaling, and unit conversions.

How This Is Calculated

A:B simplified by dividing both by their GCD; A:B = C:D solved as D = (B × C) ÷ A

4:6 simplifies to 2:3. In the proportion 4:6 = 10:D, D = 15.

Assumptions

  • The proportion solver assumes all four values maintain the same ratio (A:B = C:D).

Frequently Asked Questions

Scaling a recipe is a common example — if a recipe calls for a 4:6 ratio of flour to sugar (cups) and you want to make a batch with 10 cups of flour, solving the proportion tells you how much sugar to use.

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Last updated January 15, 2026. Results are estimates for informational purposes only — read our disclaimer.