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Is a higher density memory foam firmer?

By Jeff Frank

Density and firmness are commonly confused.

Foam density and firmness are two completely different measurements.

Most mattress manufacturers using memory foams increase the foam’s firmness as they increase density.

  • As a result the ILD (Indentation Load Deflection) “firmness” rating becomes irrelevant to their customers.

Memory foam density is measured as mass per unit volume (lb./cubic ft.)

  • The higher the density, the more foam material is used within a given volume.
  • Higher density foams will be heavier than lower density foams.
  • Higher density foams are more durable than lower density foams.
  • Higher density foams are more expensive than a lower density of the same type of foam.

Memory foams have higher densities than non-memory polyurethane foams.

  • “High density” polyurethane foams (commonly used in seat cushions) range from 1.8 – 2.8 for most residential furniture.
    • Heavier duty commercial and institutional furniture may use polyurethane foams that are 3.0 or higher.
  • “High density” memory foams (more commonly found in mattresses) begin at 5.
  • Memory foams used in mattresses can range anywhere from densities of less than 1.5 to 8 lb.
    • Most memory foam mattresses have a density ranging from 3 -5.
    • There is a significant increase in price as foam density increases.

    A foam’s firmness is measured by its indentation load deflection (ILD) rating.

    • ILD is not a straightforward measurement of “soft” vs. “firm.”
      • When comparing two foams with identical densities the one with the higher ILD will feel firmer when compressed.
      • When comparing two foams with identical ILD “firmness” ratings but different densities, the foam with the higher density will feel firmer.
    • ILD ratings for memory foams in mattresses generally range between super soft (ILD 10) to extra firm (ILD 18.)
      • ILDs of 50 can be found in memory foam used in automobile seats.
    • ILD ratings for polyurethane foams in cushions typically range from 25 – 40.

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