I agree with the others, and like Jeff said, you really need to allow enough room around each of your tools. Use the free grizzly planner and the other sites and start laying out your shop by placing the tools and equipment. I have a 30' x 40' shop and with my tools and equipment plus my wood storage and junk collections, I literally have paths to walk thru and wish I had twice the space.
I have 3 lathes (2 minis and one 1442, 2 bandsaws (1 14" with risers, 1 10" bench, one 8" jointer, one 13" planer, one 6", one 4" one 1" belt sander, table saw with 8' all around, Router table, Radial arm saw, Two miter saws, 4' x 8' assembly/work table, spindle sander, 2 scroll saws, mortiser, 4 drill presses (2 floor, 2 bench) Tormek, 5 vises plus I have two welding machines, 4' x 7' Metal work table for the welding portion, grinders, sanders, horizontal metal band saw, cutting rig, air compressors, dust collectors, cabinets and displays, desks, chairs.
Plus 3,000 bf of stickered cherry wood, 1,000 bf of stickered red oak, 1,200 bf of stickered white oak, 6,000+ pen blanks, 125 or so bowl blanks, casting pots, kits, and three large trees which have been cut and is in storage inside (sweet gum, cottonwood, mulberry) plus log sections of Pecan, Mesquite, Tallow, Elm, Willow, Cedar, Juniper, Apple, and about 1850 BF of miscellaneous wood.
LOML and I do craft shows about 18-20 weekends per year so there is almost always a lot of items in various stages. Oh we also have two 8' x 12 storage sheds crammed full.
So get the absolute biggest you can afford to get, and build it in such a way that you can easily add to later, you will probably want to.
JMHO