As such, there are no units of measurement in AutoCAD, there are conditional units and each user himself implies the necessary dimension of these conventional units (mm, cm, m, inch, foot) when creating objects in an AutoCAD document.
However, you may want to insert objects from one document into another document when document users have created objects in them in different conditional units (for example, one in millimeters and one in inches). For the correct result when inserting objects from such documents, it is necessary to perform scaling. The scale value depends on the physical meaning of the conventional unit of measure, and it is set in the Format menu item Units.
The insert Scale drop-down list selects the units in which objects are created in the current document.
The user can at any time pre-scale objects to the required units of measurement using the command SCALE (_scale). The magnitude of the scale depends on what units of measurement in which you want to translate. For example, to convert from millimeters to inches, the scale factor would be 0.03937.
You can also use the-DWGUNITS command to adjust the units and scale to the selected units.