When you\u2019re shopping for the best mattress<\/a>, you\u2019re likely to encounter the term \u201cdensity\u201d as it relates to memory foam. Density can be a difficult concept, but once you understand it, density can tell you a lot about a mattress\u2019s likely comfort and durability.<\/p>\n In this buying guide, we discuss what density is and what memory foam is, along with the different foam densities on the market. We also explain the difference between density and firmness and answer a few frequently asked questions.<\/p>\n Density is the measure of mass in a given volume to determine how close together or far apart particles are. The denser a material is, the more it weighs per a given amount.<\/p>\n When we discuss memory foam density, we do so using units of cubic feet. Heavier foams have a higher density per cubic foot.<\/p>\n Also known as viscoelastic foam, memory foam is polyurethane foam modified to respond to heat and pressure. So when you lie down on top of a memory foam mattress<\/a>, the bed molds itself around your body weight and warmth. Once you stand up, the bed snaps back to its original shape.<\/p>\n Many owners enjoy sleeping on a memory foam mattress for the pressure relief and motion isolation it offers. As memory foam contours close to your body, it leaves no part unsupported and prevents pressure from building up. Memory foam\u2019s malleability allows it to absorb movement, which prevents you from disturbing a partner\u2019s rest or vice versa.<\/p>\n Memory foam has two big drawbacks. One is an issue with retaining body heat, which may wake you in the night if your mattress grows too hot. Many manufacturers add conductive materials to the foam such as gels, charcoal, and copper, or they substitute certain petrochemicals with plant-based chemicals to create a cooling mattress<\/a>.<\/p>\n New mattresses may have an odor in the first week, as\u00a0volatile organic compounds<\/a>\u00a0(VOCs) from the production break down upon exposure. The process of VOCs breaking down is known as off-gassing, and most mattresses lose the smell after three to seven days.<\/p>\n A foam\u2019s density can affect how much pressure relief it offers, how well it prevents motion transfer, how much heat it retains, and how long it spends off-gassing.<\/p>\n There are three foam densities\u2014low, medium, and high density. By looking at a foam\u2019s density, you can judge its probable cost, durability, and comfort level.<\/p>\n Low-density foam weighs 3 pounds or less per cubic foot. Low-density foams are inexpensive as they contain relatively little material, which also helps them to retain less body heat than other densities. However, since they contain so little material, low-density foams often wear out within 6 years and may not provide as much pressure point relief as other densities.<\/p>\n As low-density foams have short lifespans, they\u2019re not the best choice of mattress to sleep on night after night unless you\u2019re shopping on a tight budget. However, they\u2019re excellent choices for a guest bedroom. Low-density mattresses are also a good choice for children\u2019s beds, as children place less pressure on a bed than an adult, extending the mattress\u2019s lifespan.<\/p>\n Medium-density foam weighs 4 to 5 pounds per cubic foot. Medium-density foam is an excellent middle-of-the-road option\u2014it\u2019s not too expensive, doesn\u2019t retain too much heat, and molds itself close to the body for pressure and pain relief. These foams tend to have decent durability, lasting around 7 years or so.<\/p>\n High-density foam weighs 6 or more pounds per cubic foot. Of the three, high-density memory foam provides the best back pain relief and motion isolation. Many owners find it\u2019s the most comfortable option because it conforms closely to the body. High-density foam is also the most durable option, likely to last at least eight years\u2013this is why it\u2019s often used as the support layer, although you can find mattresses<\/a> with high-density foams in its comfort layer.<\/p>\n Since high-density foam contains more material, however, they are the most expensive and may need more time to off-gas. Some owners\u00a0also report long break-in periods and that high-density foams conform too well to their bodies, leaving them feeling stuck in the mattress.<\/p>\n While many customers conflate a memory foam mattress\u2019s density with its firmness, the two are not the same. A higher density foam doesn\u2019t necessarily mean a firmer mattress.<\/p>\n Instead, most companies measure a mattress\u2019s firmness using its Indentation Load Deflection (ILD) rating. An ILD rating is a measure of how much force it takes to compress a material to 25 percent of its thickness. The higher the ILD number, the firmer\u00a0the material is.<\/p>\n The ILD rating is a bit technical, which is why not every company openly advertises it. If you\u2019re interested, you may have to reach out to customer service.<\/p>\n Many companies simplify firmness ratings with a 1-10 scale, with 1 as the softest option and 10 as the firmest. This number is translated into a label such as \u201cfirm\u201d or \u201cmedium-soft.\u201d These labels are an easier way to get an idea of how a mattress feels.<\/p>\nWhat is Density?<\/h2>\n
What is Memory Foam?<\/h2>\n
The Different Densities<\/h2>\n
Low-Density<\/h3>\n
Medium-Density<\/h3>\n
High-Density<\/h3>\n
Firmness and ILD<\/h2>\n