Mine is about 17 feet by 39 feet, an area of about 660 square feet. I thought it would be plenty big enough, but since building for woodworking I've invested in some metalwork kit too, including a milling machine, surface grinder and a Colchester lathe so the space isn't as abundant as I thought. Being a bit tidier would help, but I'm just not that way inclined. I have an adjacent shed for storage - that's a bit untidy too. Time for a good clean up. Trouble is, whatever size shed / workshop I had it would not be quite enough. I know I'm a lot luckier than many though.
K