High Density Foam Mattress Measurements and Durability

Measuring high density foam involves weighing a sample of foam, measuring its dimensions, and using the data to calculate a value.
Density - the measurement of mass per unit of volume expressed in pounds per cubic foot (pcf).
*Note – it is common for mattress retailers to express density simply as a number of pounds (lb or lbs). For example a 5lb high density foam mattress indicates a foam density of 5 pounds per cubic foot.
Foam density is widely regarded by foam manufacturers as the main factor determining the durability of a high density foam mattress. Durability is the ability of foam to retain its original comfort and support characteristics. In general, higher density beds are more durable. They are also more expensive to produce due to greater material content.
Foam is available in a range of densities, from 0.8 pcf to 6.0 pcf. Foam mattresses utilize foams from 1.8 pcf to 6.0 pcf.

Density and Firmness

Our intuition tells us that dense foam is firm foam. But this is the most common misconception among consumers shopping for a high density memory foam mattress.
In fact density is not directly dependant on firmness. For example, a 5 lb density memory foam mattress can be softer than a 4 lb density memory foam mattress.  Foam firmness is expressed as an ILD rating.

The Perfect Density for a Memory Foam Mattress

Foam is made up of thousands of tiny cells. The cells are formed by a polyurethane wall and filled with space (air). Higher density foams have thicker cell walls and less space inside. Lower density foam has thinner walls, greater space. If foam were made too dense, its cell walls would be too thick / stiff. It would be hard to the touch and would not conform to the body properly.
It costs more to make dense foam, and at some point it can be made too dense. So there is a balance that needs to be struck between performance, cost, and durability. If a 4 lb memory foam mattress is less expensive, performs just as well as a 5 lb bed, but has less durability, then maybe you won’t want it. But if that bed will give good performance for 7-12 years, and the 5 lb bed costs twice as much and is good for 15 to 20 years, then maybe the lower density bed is the better value.
The marketplace today has gathered around a 5 lb memory foam as the optimal choice for bedding. While more expensive than lower density foams, it provides better, long term contouring support.

High Resilience Foam Base

The base foam used in foam mattresses is known as high resiliency (HR) foam. It is a completely different animal than memory foam. Its function is to provide medium firm to firm “cushioning” support. Memory foam contours the body; HR foam reduces pressure at the points of greatest weight (hips and shoulders).
HR foam density normally ranges from 1.8 lb to 2.5 lb in mattress applications. HR foam is a more durable foam than memory foam. Even though it has a lower density, it will last as long as, or longer than, the memory foam it is combined with.