# Specifying Units of Measurement

You can specify the units of measurement for global variables, and for the values and equations that define the global variables. You can define the units in the Equations and Modify dialog boxes for dimensions, and in PropertyManagers that support equations.

Assigning units of measure in equations ensures that you do not need to edit the equations if you change the unit of measure property of a document. It also allows you to create equations that mix values with different units of measurement.

For example, you can create a global variable `Length` and define it by the equation: `=100in + 3mm + 5cm`. The equation includes values with three different units of measurement. If the unit of measurement of the document is inches, then `Length` evaluates to 102.087in. If you change the unit of measurement of the document to millimeters, then `Length` automatically evaluates to the value of 2593mm. You do not need to edit the equation, or be concerned that the size of the part will change.

If the part or assembly has multiple configurations, you can also specify a different unit of measurement for each configuration. For example, you can have one configuration where a global variable is expressed in millimeters and another where it is expressed in inches.

In the Equation and Modify dialog boxes, type-ahead lists help you assign a valid unit of measurement to each value in an equation.