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When shopping for foam-based mattresses, you will likely come across density specifications for some models. Density, a weight measurement, can be used to indicate how firm a mattress will feel to sleepers; it is calculated by determining the mass of a one-cubic-foot section of the mattress, and expressed in pounds per cubic foot (PCF). This page will discuss how foam density affects firmness, durability, price, and other mattress factors.
The term density refers to an object’s mass or weight per unit of volume; to calculate density, simply divide an object’s mass or weight by the total number of volume units. Density measurements are expressed in the following way: [units of weight] per cubic [unit of volume].
When it comes to mattress foam, density is almost always expressed in pounds per cubic foot (or PCF). Let’s say a unit of mattress foam has a density of five pounds per cubic foot; this simply means that each cubic foot of the foam weighs five pounds. If you multiply the density by the total number of volume units, you can calculate the overall weight of the mattress.
Generally speaking, mattress foam density is divided into three categories:
Density is also linked to ‘temperature sensitivity’, which refers to the way foam conforms to a sleeper’s body when it is warm or cold. High-density foam is considered the most temperature sensitive because it conforms very closely when it is warm, and offers little to no conforming when it is cold. Low-density foam, on the other hand, is less sensitive to temperature changes; its conforming abilities will not significantly change whether it is warm or cold.
The terms ‘low-density’, ‘medium-density’ and ‘high-density’ are associated with specific density measurement ranges. However, it’s important to note that the measurement ranges vary by foam material. The table below lists the density measurement ranges for the two most popular mattress foam materials, conventional polyfoam and memory foam.
|Material||Low-Density Range||Medium-Density Range||High-Density Range|
|Conventional Polyfoam||Less than 1.5 PCF||1.5 to 1.8 PCF||More than 1.8 PCF|
|Memory Foam||Less than 4 PCF||4 to 5 PCF||More than 5 PCF|
In addition to foam density, many mattress manufacturers list the indentation load deflection, or ILD, of foams used in their products. ILD indicates how much pressure is required to make an indentation in a mattress foam layer, and can be used to evaluate firmness; the higher the ILD, the firmer the mattress. ILD measurements for polyfoam mattresses typically range from 24 to 45, while the ILD for memory foam mattresses ranges from 10 to 20.
Density and ILD are often used interchangeably, but it is important to distinguish between these two measurements: density calculates mass per volume unit, whereas ILD only indicates how firm or soft the foam is. ILD has no bearing on foam density; a low-density foam could have a high ILD, or vice versa.
Density can impact mattresses in many ways. The following table compares low-, medium-, and high-density foams based on price, durability, heat retention, and other performance factors. All ratings and figures have been generated using authentic customer experiences with foam-based mattress brands.
|Owner Satisfaction||Fair||Good||Very Good|
|Average Lifespan||5 to 6 Years||6 to 7 Years||7 Years or Longer|
|Average Price (Queen)||Less than $1,000||$1,000 to $1,500||More than $1,500|
|Conforming||Fair to Good||Good||Very Good|
|Back Pain and Pressure Relief||Good||Good||Very Good|
|Motion Isolation||Good||Very Good||Excellent|
|Heat Retention||Good||Fair||Poor to Fair|
|Sex||Fair||Poor to Fair||Poor|
|Average Weight||60 to 80 pounds||80 to 100 pounds||100 pounds or more|
Your body weight can help determine which mattress density is best for you. Generally, those who weigh 130 pounds or less tend to feel most comfortable on low-density foams; medium- and high-density foams do not conform as closely under sleepers with below-average weights, and the result is often more back pressure. Likewise, heavyweight sleepers tend to sink further on high-density foams, which can cause discomfort.
The table below compares foam density types based on three different weight classes.
|Foam Density||Lightweight Sleepers (130 pounds or less)||Average Weight Sleepers (130 to 230 pounds)||Heavyweight Sleepers (230 pounds or more)|
Ease of movement is another factor. Because high-density is so sensitive to temperature changes, the material conforms more closely to sleeper’s bodies. This can be beneficial to those with back pain or pressure, but others complain of a ‘sinking feeling’ when the foam is too warm and difficulty getting off the mattress. Low-density foam, on the other hand, is easier to get on or off, but it will not conform as closely (or alleviate as much pressure) as most medium- or high-density foams.
In order to find the right mattress for them, shoppers are encouraged to understand the role density plays in a foam mattress and research the density specifications of different models. Most mattress manufacturers list foam density in their product specifications. Shoppers should reach out to customer service representatives if this information is not available.
Density also plays a role in the construction of latex mattresses. To learn more, please visit our How Is Latex Density Measured? page.