Ratio Calculator

How to use Ratio Calculator

1. To simplify, type a ratio such as 12:18:24 (two to six terms, decimals allowed).
2. To scale, enter a ratio, say which term you know and its real value.
3. To solve a proportion, fill in three of the four boxes A, B, C and X and leave one empty.
4. Read the answer and the formula shown under each card.

What a ratio tells you

A ratio compares quantities of the same kind. The ratio 3:5 means that for every 3 parts of one thing there are 5 parts of another. Because only the relationship matters, you can multiply or divide all terms by the same non-zero number without changing the ratio; 3:5, 6:10 and 30:50 are equivalent.

Simplifying finds the smallest whole-number version. A unit form where the first term is 1 is also shown, which is useful when you need to say that something is, for example, 1 : 1.5.

Scaling and proportions

Scaling multiplies every term by one factor. If a paint mix is 3 parts base to 5 parts tint and you know you want 45 of the first term, the factor is 45 / 3 = 15 and the full mix becomes 45 : 75.

A proportion states that two ratios are equal. If 3 is to 4 as 15 is to X, then 3 × X = 4 × 15, so X = 20. The solver rearranges the same relationship for whichever value is missing.

• Recipes: scale ingredient quantities to a different number of servings.
• Maps and models: convert between drawing and real distances.
• Mixtures such as concrete, fuel or cleaning solutions.
• Comparing prices or rates per unit.

Limits

Terms must be zero or positive. A ratio with a zero term can be simplified but cannot be scaled from that term. Results are rounded for display, not for further use, and the tool runs entirely in your browser.

Why use this ratio calculator tool

• Lowest terms. Divides every term by their greatest common divisor, including ratios with decimals and up to six terms.
• Scale by one value. Know one quantity and find all the others, handy for recipes, mixes and maps.
• Any unknown. The proportion solver finds whichever of the four values you leave blank.
• Clear errors. Division by zero and negative terms are caught with a message instead of a wrong number.

Frequently asked questions

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