I generally use PDF, so I print the page to measure accurately, then poster-print them at a suitable scale to be table use size - that said, I use 1/2" squares, and most maps in adventures I've used are 1/5", 1/4", 1/2", 5mm, or 10mm... and I'm aiming for 12.7mm. 1/5 is 250%, 1/4 is 200%, 1/2...