What is memory foam density?

What is memory foam?

Did you know that memory foam was originally developed by NASA in 1966? This open-celled, temperature sensitive foam has the unique capability of matching any pressure put against it, while slowly returning to its original shape when the pressure is removed. Its use eventually spread to football helmets, medical equipment, motorcycle saddles, and even bullet proof vests.

Memory foam mattresses have long been used in hospital settings for their ability to reduce pressure on patients who are immobile for long periods of time. Other medical uses include pillows, padding, and support for people with long-term pain or posture issues. Because of this material’s unique characteristics, memory foam is an ideal choice when manufacturing household mattresses.

What is memory foam density?

Lower density foams tend to have larger cells whereas higher density foam cells will be smaller - Mdiproducts (Own work) [Public domain], via Wikimedia Commons

Memory foam density is measured as mass per unit volume. Simply put, the denser the foam, the more foam material used in a given area, and the heavier that foam is.

Due to its construction, memory foam is denser than other, standard polyurethane foam, making it more supportive and durable. Memory foam used in mattresses are typically manufactured in densities ranging anywhere from less than 1.5 lb/ft3 to 8 lb/ft3. Very high density foams range from six pounds and higher; lower density memory foams are usually categorized at three pounds or lower. It’s important to know about the effects of mattress density because it impacts the longevity, durability, and support of your mattress. Most memory foam has the same chemical make-up, but a high density mattress will have a much better longevity. The longevity is an attribute of a mattresses firmness, however; density is not to be confused with the firmness (or “feel”) of a mattress.

Does density affect firmness?

Just because a mattress is manufactured at high density does not necessarily mean it will feel firm. Conversely, a low density mattress will not always feel soft.

Comfort levels of mattresses are measured by a foam’s indentation force deflection (IFD) rating. It's also commonly referred to as an indentation load deflection (ILD) rating. This indentation factor calculates the force required to make a 1 inch dent into a 50 square inch section of memory foam; the more force required, the higher the IFD rating. Most mattress comfort layers range from 3 to 5 lb/ft3 but can have vast differences in firmness because of their IFD rating. Basically, while a foam's density can affect firmness up to a point, a mattress’ firmness is influenced more by the foam's IFD and mattress layer composition. Being able to offer different IDF ratings combined with high-density foam, you can have diverse, distinct firmness levels with the consistent quality that high density foam offers.

What else does density affect?

The handprint demonstration is a good way to see memory foam's unique response time properties - Johan (Own work) [CC-BY-SA-3.0], via Wikimedia Commons

How do the different densities compare?

Low and high densities both have advantages and drawbacks. But depending on your sleep preference, a certain level of density might work better for you.

Density comparison

Popular brands that use high density memory foam

Numerous brands utilize memory foam in their mattresses, but the number of models offered, density used, and firmness options differ greatly.

Brand comparison