Measure plane works basically the same way as the quick measure. The difference here is that you first create a clip plane and then choose where you want to measure from.
The measuring tool easily finds the center of the pipe and measures out to the nearest points. In this case, it is measured to the walls. up to the ceiling and down to the ceiling. Then the target is moved so that you get the distance down to the floor instead.
On the other pipe it is measured in the same way, but straight down to the floor as there is no ceiling there.
Simple measurements are taken here from wall to wall and from floor to ceiling.