Ratio Calculator
Simplify a ratio, share an amount in a ratio, or find the missing number in a proportion.
What a ratio says
A ratio compares quantities by their relative size. A concrete mix of 1:2:3 (cement : sand : gravel) means that for every 1 part of cement there are 2 parts of sand and 3 of gravel, whatever the unit, as long as every part uses the same one.
Simplifying a ratio
Divide every part by the greatest common divisor. For 12:18:24 the GCD is 6, giving 2:3:4. Decimal parts are scaled up first: 1.5:2 becomes 15:20, which simplifies to 3:4.
Sharing a total in a ratio
Share of each part = Total × part ÷ (sum of all parts)
Example: split 900 in the ratio 2:3:4. The parts add up to 9, so one part is worth 900 ÷ 9 = 100. The shares are 200, 300 and 400. Check: they add back up to 900.
Solving a proportion
If A : B = C : x, then x = B × C ÷ A
Example: a recipe uses 2 cups of flour for 3 eggs. For 10 cups of flour you need 3 × 10 ÷ 2 = 15 eggs. The same calculation scales map distances, dilutions and screen sizes.
Common questions
Is a ratio the same as a fraction?
Related but not identical. In a ratio of 2:3, the first part is 2/5 of the total, not 2/3, because the whole is 2 + 3 = 5 parts. Use the split tool above to see each part's share of the total.
Does the order of a ratio matter?
Yes. 2:3 and 3:2 describe different mixtures. Keep the parts in the order the ratio names them.
What about aspect ratios like 16:9?
They work the same way. For a 16:9 screen 1920 pixels wide, the height is 9 × 1920 ÷ 16 = 1080 pixels. Use the proportion solver with A = 16, B = 9 and C = 1920.