Vertoq
Ratio Calculator
Enter two numbers to see the ratio in its simplest form, and a third number to solve for the missing term in the proportion.
What a ratio shows
A ratio, written a:b, compares the size of two quantities. 2:3 means that for every 2 units of the first thing, there are 3 units of the second, regardless of the actual sizes involved, a ratio of 200:300 means exactly the same thing as 2:3.
Simplifying a ratio
Just like a fraction, a ratio is simplified by dividing both numbers by their greatest common divisor. 4:6 has a GCD of 2, so both 4 and 6 divide by 2 to give 2:3, the same ratio in its simplest form.
Solving a proportion
A proportion states that two ratios are equal: A:B = C:X. To solve for the missing number X, multiply B by C and divide by A: X = (B × C) / A. For example, if a recipe calls for flour and sugar in a 2:3 ratio, and you have 5 cups of flour, the sugar amount is (3 × 5) / 2 = 7.5 cups.
Common uses
Ratios and proportions are used to scale recipes, mix paint or chemicals to the right concentration, convert map scales, and compare size relationships in everything from finance to design.
Frequently asked questions
What's the difference between a ratio and a fraction?
A ratio compares two separate quantities (like 2 cats to 3 dogs), while a fraction shows a part of a whole. They're calculated similarly but mean different things.
Do Term A and B have to be whole numbers?
No, but simplifying to the smallest whole numbers only applies to whole numbers. With decimals, the ratio is shown as entered, without simplification.
How do I solve a proportion if I want to find A instead of X?
Rearrange which numbers you enter, if you know B, C, and X but are looking for A, enter them in the corresponding fields and read off the simplified ratio, or rework the formula by hand: A = (B × C) / X.