The Measure tool toggles measurement mode, enabling you to measure distances on a model.

Click on the model at the point from which you would like to measure. Click again on the model at the point to which you want to end the measurement.
The coordinates of each point, distance measured, and vector are instantly updated
Measuring distances on the model using the Measure tool
to access the tool from the ribbon. Alternatively, you can access it from the Navigation bar. The Measurements dialog appears.To access this dialog select
Measure from the Navigation bar or the View tab of the ribbon. Alternatively, right-click on anywhere on the model and select Measure from the context menu.
To make a measurement, click anywhere on the model to set the start point. Then click a second point on the model to set the end point.