Ratio Calculator
A ratio compares two amounts. This calculator simplifies a ratio, and when you know three numbers in a matching pair, it finds the fourth. Simplify, scale and solve a to b equals c to d.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
To simplify, divide both sides by their greatest common factor. To solve a:b = c:d for the missing d, multiply b by c and divide by a.
Keep both pairs in the same units, or the answer will not match what you expect.
Worked example
The ratio 3 to 4 simplifies to 3 to 4. Scaling 3 up to 9 means scaling 4 up to 12.
Questions
Do the first two numbers have to be whole?
The simplified ratio works with whole numbers, because it looks for a common factor. The solving step works with any numbers above zero.
What is a common factor?
A number that divides evenly into both. The greatest common factor is the largest one, so dividing by it leaves the smallest pair of whole numbers.
Can a ratio be written with a colon?
Yes. A colon and the word to mean the same thing, so 3:4 and 3 to 4 are equal.
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- Percent Difference CalculatorGap between two values, as a share of their average.
- Standard Deviation CalculatorSpread of a list of numbers.
- Weighted Average CalculatorAverage where some values count more.
- Median CalculatorMiddle value of a list of numbers.