Here's a chart generated from the scripts for the MSD-style information displays in my LCARS system. It's often hard to get good information, and maybe I can get some help here.
I have a gallery of those displays here (with these figures near the bottom of each screen), although I haven't updated the gallery with the latest changes in figures for mass taken from two recent Trek Tech
threads from the last couple of days yet. The chart below, however, does show those latest figures.
Gallery: Starfleet Schematics
The dimensions for the Nebula class are based on it's having the same saucer width as the galaxy class, despite the variety of figures for that around the Web.