Ratio Calculator
Simplify ratios, solve proportions, and scale ratios up or down.
Enter two numbers to reduce the ratio A:B to its lowest terms. Decimals are supported.
What is a Ratio?
A ratio compares two quantities, showing how many times one value contains another. The ratio of A to B is written as A:B (or A/B). For example, if a recipe uses 2 cups of flour for every 3 cups of water, the flour-to-water ratio is 2:3.
Simplifying Ratios
To simplify a ratio, divide both terms by their greatest common divisor (GCD). For example, 8:12 has a GCD of 4, so it simplifies to 2:3. You can also express a ratio in decimal form (A ÷ B) or in the normalized 1:n form by dividing both sides by A.
Solving Proportions
A proportion states that two ratios are equal: A:B = C:D. When one term is unknown, you can solve it using cross-multiplication, since A × D = B × C. For example, in 2:5 = 6:D, we get D = (5 × 6) ÷ 2 = 15.
Tip: Ratios stay the same when both terms are multiplied or divided by the same non-zero number. This is why 1:2, 2:4, and 50:100 all represent the same relationship.