1. On the Home tab click the arrow next to Measure.
2. Click Diameter. The Measure: Diameter toolbar appears.
3. Click on the toolbar to expand the Measure: Diameter dialog box.
4. Under Setup select a surface. The diameter is calculated and displayed in the Results area, the measurement panel, or both.
5. To measure the diameter at a specific location on the surface, click the Point collector and select a datum point or a point on a face, curve, or an edge.
Measure.
Diameter. The Measure: Diameter toolbar appears.
on the toolbar to expand the Measure: Diameter dialog box.