Glossary
Foam density (lb/ft³)
The weight of one cubic foot of foam, in pounds — the single best objective predictor of how long a foam layer lasts. For comfort-layer polyfoam: under 1.5 lb/ft³ is low, 1.5–1.8 is medium, 1.8+ is high. For memory foam: under 3.5 is low, 3.5–5 is medium, 5+ is high. Brands rarely advertise density on low-density beds — the omission is itself a signal.
Related: polyfoam · memory foam · body impression