Ratio and proportion calculator
A proportion reads a : b = c : d (a is to b as c is to d). Pick the unknown term and enter the other three.
Result
15Missing term d
- Full proportion
- 2 : 3 = 10 : 15
- Simplified ratio a : b
- 2 : 3
- Ratio value a ÷ b
- 0.666667
- Scale factor c ÷ a
- 5
Inputs
- Unknown term
- d
- a
- 2
- b
- 3
- c
- 10
How it is calculated
In a : b = c : d, the cross products are equal: a × d = b × c.
Result
Missing term d
- Full proportion
- 2 : 3 = 10 : 15
- Simplified ratio a : b
- 2 : 3
- Ratio value a ÷ b
- 0.666667
How it is calculated
- In a : b = c : d, the cross products are equal: a × d = b × c.
- Missing term: d = b × c ÷ a, c = a × d ÷ b, b = a × d ÷ c, a = b × c ÷ d.
- To simplify a ratio, divide both terms by their GCD.
Example
2 : 3 = 10 : d, so d = 3 × 10 ÷ 2 = 15. Simplified ratio 2 : 3, scale factor 5.
Good to know
- The term used as a divisor cannot be 0.
- The simplified ratio is only given for numbers with at most 6 decimals.
- Negative numbers are accepted; the minus sign goes on the first term of the simplified ratio.
Frequently asked questions
What is this tool used for?
A proportion reads a : b = c : d (a is to b as c is to d). Pick the unknown term and enter the other three.
How is the result calculated?
In a : b = c : d, the cross products are equal: a × d = b × c.
What should I check before using the result?
The term used as a divisor cannot be 0.