Measuring Entities 
To measure entities, measure must be enabled, as shown in the status
bar:
Measure enabled
Measurement not allowed
To enable measurement, publish or save the file from your CAD application
with the Enable
measure option selected.
To measure entities:
Click Measure
or Tools, Measure.
On the Measure
tab, choose Selection Filters,
and specify Units.
Select
entities in the graphics area.
Entities are
displayed in red to indicate they will be selected if you click the mouse.
The selections
are listed under Selected Items.
Results appear on the Measure
tab and in callouts in the graphics area.
To
release the Measure tool, click
it, click Select 
, or press Esc.
The measurements
disappear. Measurements are not saved with the file. To create markup
dimensions to save, see Dimensions.
Selection Filters
Select one or more filters. If
no filters are selected, you can select any measurable entity in the graphics
area.
Select Face
Select Edge
Select Vertex
Select Hole
Selected Items
When you select an entity in
the graphics area, a name such as edge<1>
or point<3> appears in the
list.
To delete items from the list,
select an item and press Delete.
Click in the graphics area (not on the model or view) to clear the list.
Units
Specify Distance
and Angle units. Measurements
are converted to the selected units.
Results
Results are displayed with: