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Ratio Calculator
Check a proportion in the form X : Y = A : B (same as X / Y = A / B). Enter all four terms as text; RapidRatio compares BigNumber cross products (X·B vs Y·A) and shows true or false—your inputs are never auto-filled or changed ( core-engine.js).
Check proportion
Result
How To Use The Ratio Calculator
A proportion says two ratios describe the same relative scale—like matching a map distance to real ground. Algebraically, X : Y = A : B means X / Y = A / B, which rearranges to the single equation X·B = Y·A (cross-multiplication). Follow these three steps:
- Write the proportion—place the four values you already have in the pattern X : Y = A : B, matching each slot to the same quantity on both sides of the equals sign.
- Multiply across the equals sign—multiply the diagonals that face each other: X with B, and Y with A. Equivalent ratios satisfy X·B = Y·A.
- Compare the products—if the two BigNumber products match, the statement X:Y = A:B is true; if not, it is false. This tool performs that comparison only—it does not change your inputs.
Precision and validation
Inputs are parsed as strings into BigNumber; the two cross products use the same 14-digit fixed display and trailing-zero trim as other RapidRatio tools. Invalid numbers surface as an error in the result strip; false is not an error—it simply means the products differ.
FAQ
How do you solve a 4:5 ratio?
A written ratio like 4:5 on its own only names two parts relative to each other; it is not a full “equation” you can solve until you pair it with a second ratio or a total. In practice you embed it in a proportion—for example 4:5 = 12:x—and then cross-multiply (4·x = 5·12) to isolate the unknown.
What is the Ratio Calculator used for?
You use it to see whether two ratios are equivalent—enter all four terms for X:Y = A:B and read true or false from comparing cross products. That is useful for homework checks, recipes, maps, and any quick yes-or-no on proportionality without changing what you typed.