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Ratio Calculator

Solve missing values in a ratio (A:B = C:?) or simplify a ratio to its lowest terms.

  1. Enter your numbers
  2. Results update as you type
  3. Copy the answer or share the link
Runs in your browser. Your data and files never leave your device.

About the Ratio Calculator

Scale a ratio up or down — for recipes, mixtures, maps, screen sizes and aspect ratios — or reduce it to its simplest form.

How does the Ratio Calculator work?

Two ratios are equal when their cross-products are equal: A × D = B × C. So the missing value D = B × C ÷ A. Simplifying divides both terms by their greatest common divisor.

Ratio Calculator formula

A : B = C : D  ⇒  D = B × C ÷ A

Example

A 16:9 screen that is 1920 pixels wide is 1920 × 9 ÷ 16 = 1080 pixels tall.

12:18 simplifies to 2:3.

Frequently asked questions

How do I split an amount in a ratio?

Add the parts, divide the amount by the total and multiply by each part. $600 split 2:1 is $400 and $200.

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