How to use Ratio and Proportion Calculator
- Choose Simplify a ratio or Solve a missing value in a proportion.
- For a ratio, type terms separated by colons, such as 12:18.
- For a proportion, mark the unknown x, such as 2:3 = 8:x.
- Set the decimal places. The answer updates as you change the values.
Example: Ratio and Proportion Calculator
Simplify a ratio to its lowest terms.
Options
- What do you want to do?
- Simplify reduces the terms to the smallest whole numbers with the same relationship. Solve finds the one term marked x.
- Ratio terms
- Separate 2 to 12 terms with colons or commas. Decimal terms are read as exact fractions, so 0.1:0.2 gives 1:2 without rounding.
- Proportion with one missing value
- Used in the solve task. Each side needs two terms, and exactly one of the four positions is x.
- Decimal places
- 0, 2, 4, 6 or 8. This rounds the decimal version of an answer that is not whole; the fraction behind it stays exact.
Supported inputs and limits
Where your input is processed
This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.
The unit stays outside the ratio
Simplifying 12:18 to 2:3 changes the scale, not the relationship. If the numbers describe grams or litres, keep the unit with the original quantities, because 2:3 alone does not say what is compared. The unit also lets you check the answer: 12 g to 18 g and 2 scoops to 3 scoops follow the same proportion but are not the same statement.
Cross multiplication keeps one unknown simple
A proportion such as 2:3 = 8:x says two ratios are equal. Cross multiplying gives 2 * x = 3 * 8, so x = 12. With the unknown in one position the equation stays linear and has one solution, and the tool writes the cross multiplication out and checks both sides.
Questions about Ratio and Proportion Calculator
Can a ratio contain decimals?
Yes. 0.1:0.2 simplifies to 1:2, because each term is read as an exact fraction and the shared scale is removed rather than rounded.
Which position can the missing value take?
Any of the four. In 3:4 = x:12 the answer is x = 9, and in 6:7 = 18:x it is x = 21. One x per run.
What does Total parts mean?
It is the sum of the simplified terms. The ratio 2:3 has 5 parts, the figure you use when splitting a quantity into shares.
Why is 0:0 refused?
Every term is zero, so there is no common divisor to remove and no relationship left to describe. At least one must be above zero.