Ratio Calculator
Choose what you want to do with a ratio: reduce it to lowest terms, find the missing term of an equivalent ratio, or divide an amount in that ratio.
Result
- A ÷ B
- 0.666667
- As 1 : n
- 1 : 1.5
- As n : 1
- 0.6667 : 1
- Shares of the whole
- 40% and 60%
Formula
- Simplify: divide both terms by their greatest common factor
- A : B = C : D means A × D = B × C, so D = B × C ÷ A
- Share of a total: total × A ÷ (A + B) and total × B ÷ (A + B)
How the Ratio Calculator works
A ratio compares two quantities. It is in simplest form when the two terms share no common factor other than 1. To get there, divide both terms by their greatest common factor.
Two ratios are equivalent when cross-multiplying gives equal products. That property lets you find a missing term, which is how recipes are scaled and maps are read.
Worked example
12 : 18 has a greatest common factor of 6. Dividing both terms by 6 gives 2 : 3. To extend it, 12 : 18 = 30 : ? gives 18 × 30 ÷ 12 = 45.
Frequently asked questions
How do I simplify a ratio with decimals?
Multiply both terms by 10, 100 or more until they are whole numbers, then divide by their greatest common factor. 1.5 : 2.5 becomes 15 : 25, which simplifies to 3 : 5.
How do I split an amount in a ratio?
Add the terms to get the number of parts, divide the amount by that, and multiply by each term. 100 split 2 : 3 is 5 parts of 20, giving 40 and 60.
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Calculations run in your browser and nothing you enter is sent to a server. Results are provided for general information. Check critical figures independently before relying on them.