Depending on your location and type of design, you may prefer different units as the default when creating a model. For example, a woodworker in the United States may prefer Feet and Inches as the default, whereas a machine designer in Germany may prefer millimeters.
Step 1: Open a new Part Workspace
Click the New Part icon on the Home Window.
Step 2: Click the Gem Menu on the top left and select Properties
Step 3: Click the General option under Units.
Step 4: Select the Unit dropdown under the Length section and choose the length units you prefer to work in.
Step 5: Select the Unit dropdown under the Mass section and select the mass units you prefer to work in.
Step 6: Click the checkbox for the Set current settings as the default settings for parts, sheet metal, and assemblies option at the bottom left of the dialog.
Step 7: Click Apply
Now any dimensions you create or mass you query will be in the appropriate units while in a 3D modeling environment.