Ratio Calculator

A ratio compares two quantities by division. Written A : B, it expresses how big A is relative to B. For example, a ratio of 12 : 18 says that for every 12 units of the first quantity there are 18 units of the second. The decimal form, A ÷ B, is the size of A per unit of B.

Divide both sides by their greatest common factor. For 12 : 18, the GCF of 12 and 18 is 6, so the simplified ratio is 2 : 3. A ratio is in simplest form when its two sides share no common factor other than 1.

Two ratios A : B and C : D are equivalent exactly when A × D = B × C (cross multiplication). For example, 2 : 3 and 4 : 6 are equivalent because 2 × 6 = 3 × 4 = 12. The calculator runs this cross-product check whenever a second ratio is entered.

A fraction A/B is one number: the value of A divided by B. A ratio A : B compares two quantities and is most useful as a comparison, like a recipe (2 parts flour to 1 part sugar). Numerically they are equivalent: 2 : 3 means the same as 2/3 when used as a value.

One side can be 0, which means that quantity is absent. The ratio 0 : 5 simplifies to 0 : 1. Both sides being 0 is not a defined ratio and the calculator flags it.

Yes, but ratios are most useful with whole numbers. With integer inputs the calculator returns the simplest whole-number ratio. With decimal inputs it still computes the decimal and percent form, but the simplified line just echoes the input since there is no clean integer reduction.