Ratio Calculator

This calculator handles two common ratio problems in one tool: reducing a ratio to its simplest form, and solving a proportion when one value is missing. In the first section, enter any two numbers as A and B and the calculator instantly divides both by their greatest common factor to show the simplified ratio, for example 12:18 reduces to 2:3. In the second section, you work with four boxes set out as two equal ratios, such as 2:3 equals 8 to a missing value. Fill in any three of the four boxes and leave the one you want to find blank, and the calculator cross multiplies the known values to solve for it, returning the missing value straight away. Both results update live as you type, so you can try different figures without clicking a button. This is useful whenever you need to scale something up or down while keeping the same relationship between two quantities: adjusting a recipe for more or fewer servings, mixing fuel and oil or paint to the right strength, resizing a scale drawing or map, splitting money or shares between people in a fixed proportion, or checking that two ratios are actually equivalent. Enter whole numbers or decimals in either section, and use the worked example below as a guide if you are unsure which box to leave blank.

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