Sealy posturepedic mattress come in a range of different depths and so it can be a little confusing knowing what is best for you. Although often overlooked, the depth of a mattress it just as important as the type of mattress. They can range from anywhere between four to 29 inches in depth, with the most popular mattress being six inches thick. What you need to keep in mind is that mattress depth is directly linked to the weight of the person lying on it.For more information, please read our mattress buying guide.