Each map board is 8.5" x 11". Most scenarios use 2-6 boards, with a few using more. You could easily play a majority of the scenarios with a 30" x 30" table, though any 3x3 map setups or 4x(anything) would be problematic. For Screaming Eagles, 2/18 would be problematic, 5/16 for Ghost Panzer, 1/12 for Texas Arrows, and 3/10 for the bonus scenario pack.
You also need a small amount of space for a counter tray, a place to roll dice, the rulebook and scenario book. Most of that could be set on a chair next to the table.