A popular tool that has caught a few users out over the past year in SOLIDWORKS 2013
has been the Measure Tool and in particular not being able to access various options within it. The reason for this is typically because the 2nd box in my image (Point to Point) is selected.
Deselecting this option allows you to use the first drop down menu and take advantage of:
Center to Centre
Hopefully these options will help you check those important dimensions.
Simon Beamish Elite Applications Engineer