That depends on the bracket.
Model 9594 brackets have a wall mount minimum of 16" Wide x 20" High
Model 1044 is the same, but you'll want to keep in mind that if you are mounting it to a wall with studs you have to connect two studs using two 2x4's horizontally. Studs are generally 16 or 24 inches from center of stud to center of stud. I recommend downloading the bracket instruction manual for more details.