Back Sleepers: These sleepers lie on their spine, so they tend to prefer firmer mattresses in the 6-7 range.
Stomach Sleepers: Stomach sleepers need a medium-firm mattress to support spinal alignment in the neck. Depending on the weight of a sleeper, a firmness of 5-7 is recommended.
Side Sleepers: These sleepers need a softer mattress that contours to the body to keep the spine in a straight line. Mattresses in the 4-6 range are usually the best.
Combination Sleepers: Most of us are combination sleepers. A medium-firm mattress of a level 6 is a good option for balanced support and pressure relief.