I would suggest not having the grid show on the map, or if you have the option in your image editor, keeping the grid on a separate layer so that you can output a copy without one. It will make final placement much simpler if you don't have to mess with a pixel-level matching. The simplest thing is to decide how you want the overland map to function. Is there a point to having a grid at all? If you want to be able to measure daily travel or something, then maybe a 20 mile grid. If you want to measure a town map then figure out a convenient measurement scale. Once you have that in mind, figure out how many units that should be on your map. For instance, if you want a 20 mile per unit map, and the map measures 300 miles by 200 miles, you want a final image that is determined by that size. If you usually view your map on screen at 100% and don't care if there's a little fuzziness at magnification, that's 70 pixels per grid unit, or 1050x700 pixels. Your map should completely fill a 30x20 page. Snap and go. If you want more resolution, up the final pixel output accordingly. 140px/un gives you 2100x1400 pixels. Don't worry about dpi. That's a complete misnomer. At no point are you outputting to paper, so "inch" means nothing. Your measurement here is grid unit based. Hexes are a little harder to figure, so just worry about the "across the hex" dimension, the other dimension can fall where it will so long as you scale proportionately, and you can adjust the final page size to match. One final caveat, don't try to have an overland map that's meant to be used at a tactical scale: I.e. don't run a knife fight on a map of North America. Depending on the computer, a 20x30 map is fine, a 50x50 should be OK, a 100x100 map will likely see some problems with lots of tokens, and anything greater is heading into potential danger.