Working with Markups > Measurements > 3D Measurements > To Create an Envelope Measurement
  
To Create an Envelope Measurement
1. Click Markup > Envelope. The Measure Envelope dialog box opens.
2. Select one or more entities to measure.
3. In the Setup panel, under Show, select one of the following measurement types:
Extents—Bounding box dimensions in the X, Y, and Z directions.
Corner Coordinates—Coordinate positions for each corner of the bounding box.
The results and the bounding box common to all selected parts update.
4. Click . The measurement is saved to the annotation set.