Considering the fact that my garage has an upstairs and downstairs and combined they are approx 800 sq/ft I'd say that my garage is big enough for the time being.
I have to disagree, i have 1500sq ft of shop space, with another 500 or so storage above it, and another 500 ft of garage at my house. All crammed full of shit.
I'm thinking of of an autobody shop equation that tells you how long before you get your ride back, which is to double the amount of time you were quoted, and add 1 in front of it, quoted 2 days to fix, 2x2=4 plus 1 infront of it, so 14 days. I'm pretty sure this could be use to calculate how much space you should have to have adequate room to work, have storage, and of course hang out area, i currently have 2500 of space, 2x2500=5000, add one in front, 15000sq ft. Sounds about what i need to have a proper work area.