Choose Inspect tab→3D Measure group→Minimum Distance .
Click the first element.
Click the second element.
Tip:
To measure in tight spots, you might want to zoom in on different areas of the part in different windows. You can locate and click elements in any window.
At any time during the Minimum Distance command, you can run a view manipulation command. When you exit the view command, the Minimum Distance command continues at the previous state.
In an assembly, you can activate inactive parts that you want to measure to by selecting the Activate Part button on the Minimum Distance command bar and then selecting the part.
You can select a user-defined coordinate system to define one of the points. If you use a coordinate system, the returned values will be relative to the specified coordinate system.