I have a 2 car garage. I think by building standards that's 21 feet by 21 feet. Mine is slightly wider, but has a single rollup door. At one time I had about 8 or 9 in mine. They had to be disassembled to fit, though.
Just Kidding!
If you had wheel dollies under them to move them around, you probably could get 4 inside but I'd bet some of them would be touching the wall and one another.