my first was 10x10 with no walls, dirt floor. my second was 16x14 with 3 walls, gravel floor. my third and current one is 25x45 with 4 walls, concrete floor, and insulation. Neither of my first shops were at all bad for the amount of equipment i had at the time, but as your skills grow, your tooling grows, and it sure is nice to have more space. as a general rule, i think bigger is better. i have never heard of anyone complaining of too much shop space.