What size counts as an 'extended' mouse pad?

Extended (often labeled XL, XXL, or 3XL) pads typically run from about 31 inches up to 48 inches wide and 12 to 24 inches deep, enough to sit your keyboard and mouse on the same surface. The picks here range from roughly 31.5 inches wide up to a 48-by-24-inch full-desk mat, so match the width to your desk and how much keyboard travel you want.