Density is measured by weighing one solid cubic foot of foam material. Density equals how many pounds per cubic foot it weighs. So when we say two-pound density foam, it means that a piece of foam 12″w x 12″l x 12″h will weigh 2 lbs.
Open cell foams for insulation typically weigh in at 0.4 to 0.7 lb./cu. ft.
Closed cell foam for insulation applications range in density from 1.7 lb./cu. ft. to 2.6 lb./cu. ft.
Foam for roofing applications typically use a 2.5 to 3.0+ lb./cu. ft. to support traffic and loads better.
The higher the density of the foam, the heavier, or stronger it becomes. Some polyurethane foams are molded into decorative interior molding and painted or stained for a simulated wood effect. These “higher density” foams are typically in the 30 lb./cu. ft. to 40 lb./cu. ft. density range.