Measures the distance between points in free space or between key points. When you are in the middle of a task, you can measure distances using Measure Distance at any time.
When you move the pointer over a key point, the distance between the current location of the pointer and the last point you clicked appears, along with the delta values. The delta values are the distances, as measured along the x and y axes.
When you click a third point, the cumulative distance between the first and last point that you clicked appears next to the pointer.
The Measure Distance command is also available on the Dimension Toolbar.