Ratio Calculator β Simplify Ratios & Solve Proportions
Simplify ratios like a:b or a:b:c to their lowest terms with the GCD, and solve proportions a:b = c:x for the missing value. Decimals are supported.
π Runs entirely in your browser. Your input and output are never sent to a server or stored β fully private.
Simplify a ratio
Solve a proportion
Solve a : b = c : x for x
Decimals are supported and scaled to whole numbers automatically.
About this tool
This ratio calculator simplifies a ratio of two or three terms to its lowest whole-number form, and it also solves proportions where one value is missing. Type a ratio such as 12:18 to reduce it, or set up an equation like 3:4 = 9:x to find the unknown. It divides by the greatest common divisor and cross-multiplies for you, showing a clean result every time. The whole calculation happens in your browser as you type.
Frequently asked questions
How do you simplify a ratio to lowest terms?
Every term is divided by the greatest common divisor of the whole set. For 12:18 the greatest common divisor is 6, so dividing both by 6 gives the simplified ratio 2:3. With three terms such as 4:8:12 the same idea applies: dividing all three by 4 gives 1:2:3. The values keep their proportions, simply expressed in the smallest whole numbers possible.
How does it solve a proportion with an unknown?
Enter the proportion as a:b = c:x and the tool cross-multiplies to find the missing value. The rule is that a times x equals b times c, so x equals b times c divided by a. For 3:4 = 9:x, that is 4 times 9 divided by 3, which gives x = 12. It works wherever the blank sits among the four positions.
Is my data sent anywhere?
No. The calculator works entirely in your browser using simple arithmetic, so the numbers you enter stay on your device and are never sent to or stored on a server. There is nothing to install and no account to create β open the page and the simplification runs instantly.