For parts, assemblies, and presentations the template file sets the default units used in a file. For drawings, the active standard and the dimension style specified in the template file sets the units.
The template is typically a file named Standard. xxx in the template folder. The default template units are specified when you install Inventor.
To change the default unit of measure in the active file, go to Tools tab Options panel Document Settings and then select the Units tab in the dialog box. Select the Length drop-list to change units such as inches to mm. When you change the units setting, all existing values in the file display as the new units. All subsequent entries are displayed in the new units. Unit value settings are saved with the file.
You can also override the default units in any value box. For example, you can type 12mm in the dimension value box of a file using an inch unit of length. The result is displayed as 0.472, but the original 12mm unit value is retained and appears in the value box when you edit.
In drawings, the dimension style, and the active drafting standard set the units system. Edit the dimension style or drafting standard to change the units system.
All subsequent entries are displayed in the new units. Unit value settings are saved with the file.