Ratio Calculator
Simplify a ratio to its lowest terms, or solve a proportion (A:B = C:D) for the missing value.
Simplify a ratio
Simplified ratio:
Decimal value (A ÷ B):
Solve a proportion
A : B = C : D — leave exactly one of the four fields blank to solve for it.
Missing value:
Simplifying ratios and solving proportions
Simplifying a ratio works just like reducing a fraction: divide both terms by their greatest common divisor until no common factor remains. A proportion (A:B = C:D) states that two ratios are equal — cross-multiplying (A×D = B×C) lets you solve for any single missing term once the other three are known.
Frequently asked questions
Why does the simplifier handle decimals? Ratios are sometimes given with decimal values (e.g., 2.5 : 4) — the calculator scales both sides up to whole numbers first (based on the number of decimal places), then simplifies normally, so the result is still a clean whole-number ratio.
What's a real-world example of solving a proportion? Scaling a recipe: if 2 cups of flour makes 3 dozen cookies, solving "2:3 = C:5" tells you how much flour is needed to make 5 dozen — the same cross-multiplication method used in the proportion tool.
Is a ratio the same as a fraction? They're closely related — a ratio A:B can be written as the fraction A/B — but ratios are often used to compare two separate quantities (like ingredients or map scale), while fractions typically represent a part of a single whole.