Ratio Calculator

Solve a missing value in a proportion, or reduce any ratio to its simplest form.

Solve a proportion

Simplify a ratio

How to Use This Calculator

For the proportion solver, leave exactly one of the four boxes empty and press Solve. For example, to find how many apples for 8 people when 2 people share 3 apples: 2:3 = 8:?

Frequently Asked Questions

What is a ratio?

A ratio compares two quantities, like 2:3 ("two to three"). It means the first is two-thirds of the second.

How do I simplify a ratio?

Divide both numbers by their greatest common divisor. 18:24 ÷ 6 → 3:4.

What is the cross-product rule?

In a:b = c:d, multiplying across gives a×d = b×c. This is how you solve for any missing term.

Can ratios include decimals?

Yes. For proportions, decimals work directly. For simplification, results may round to 4 decimal places.

Practical Example

If a recipe needs 2:3 cups of sugar to flour and you use 1.5 cups of sugar:

Solve 2:3 = 1.5:x → x = (1.5 × 3) ÷ 2 = 2.25 cups of flour
Simplified: 18:24 → 3:4

What Your Results Mean

Simplified ratio — the relationship reduced to its simplest whole terms.
Missing term — the unknown value that keeps the proportion equal.