The number of squares on the square side is 22 x 25.
Hexes are 21/22 x 28. The width alternates between 21 and 22 hexes, so no play space is wasted.
Wet erase markers are perfect for using with Chessex Battlemats and Megamats. Water-based overhead-projection markers work best on vinyl mats as they are designed for plastic. DO NOT use grease pencils, permanent markers, or dry erase pens on the mats. The vinyl surface is too porous to allow for easy removal.