The Differences and Relationship Between Foam’s Density, Weight, and Firmness

If you were to tell a stranger that foam has density, weight, and firmness characteristics, he or she would likely understand, given how common the terms are. However, one of the most confusing things about foam is the relationship between these characteristics. On the surface, it would seem the density or weight of a material would allow you to draw a correlation about its firmness, and vice versa. In general, this is often true, but when applied to foam products, density and firmness are independent values for determining a foam’s qualities.

2.8 Pound Density HD36 Foam

2.8LB Density HD36 Foam

It would be accurate to say density is a foam characteristic that is “over-applied,” rather than one that is misunderstood. The density of foam means the same thing as any other application of the term; the quantity or mass of a material per a measurable size or volume. This pertains to all varieties of foam, including expanded polystyrene (EPS), polyethylene, polyurethane foam, and others. How density is measured varies across materials though, and in the case of foam, density is found by weighing a 12″ x 12″ x 12″ block of the material. If a product has a 3LB density, that means its 12″ x 12″ x 12″ block weighed 3LB. And while it’s vital to understand that density does not  pertain to the firmness of a foam product, it does correlate to the quality and longevity of a product.

Many conventional foams have a density between 1LB and 3LB. However, the densest materials can be as much as 10 or 15LB. High-density foam, Like The Foam Factory’s 2.8LB density HD36-HQ foam, is optimal for uses that receive heavy or daily use like couch cushions, bedding, or automobile seating. Lower density foam is excellent for occasional-use products like shipping foam, crafts, or guest room mattress toppers.

Density is also sometimes referred to as weight, whi