There are three types of carpet padding on the market: rubber, fiber and urethane foam. Each type can be further categorized by its density and weight. The density is calculated by weighing 1 cubic foot of padding. The most common padding has a density between 5 and 8 pounds. The denser the carpet pad, the longer it will last.
For high-traffic carpeted areas in the home, such as hallways, stairs or other areas, the padding should be dense and thin, no more than 3/8 inch thick. In bedrooms, lightly traveled areas or areas where a softer, more luxurious feel is desired, a thicker pad can be used. The padding in these areas can be 3/8, 7/16 or 1/2 inch thick. Generally, 6-pound padding is sufficient for residential carpets.
Berber, commercial grade and other low-pile carpets should use a firm dense pad with a thickness measuring 1/4 or 3/8 inches. An 8-pound carpet pad is recommended for these types of carpet.