Calculate Ratio
Calculate Ratio uses a simple division equation to determine the relationship between two number variables. Calculating ratios is a form of normalization, which makes it especially useful for comparing areas that are not uniform in size or population.
Note:You can also calculate a ratio using the View Data Table window.
Example
A business analyst for a consortium of colleges wants to know which states have colleges with the highest return on investment. Calculate Ratio can be used to create a ratio between the average earnings after graduation and the average cost of college.
See the Solve a spatial problem lesson for the complete workflow.
Usage notes
Calculate Ratio can be found using the Action button 
under How is it related? in the Find Answers tab. The input layer can be a point, line, or area layer.
Two number fields must be chosen as the numerator and the denominator:
- Numerator: The number that will be divided in a ratio. In the case of average household income, total income would be the numerator.
- Denominator: The number that will be used to divide the numerator in a ratio. In the case of per capita crime rate, total population would be the denominator.
Calculate Ratio adds a new rate/ratio field to the input layer. You must include a new field name to run the calculation.