Can't dimension to the edge of a sphere

What I need to do is dimension the overall length of a cylinder with a full radius on one end.  I can easily measure to the center of the radius but can't get a dimension to stick to the edge, or tangent point.  I've tried adding sketch lines, center marks, etc but nothing seems to work.  This should and probably is a very easy thing to do; can anyone help?

Thanks!

Jason

SolidworksDrawings And Detailing