Foam density and why cheap seats flatten
Comfort on day one comes from the showroom. Comfort in year three comes from foam density, and almost nobody specifies it.
Published by JP Furniture · Chair manufacturer in Foshan, China · 2026-09-26
Density versus softness
Density (kg/m³) is how much material is in the foam; softness is how it feels. They are not the same thing. A high-density foam can be soft, and a low-density foam can feel firm until it collapses.
- 20–25 kg/m³ — light domestic, backs and arms.
- 30–35 kg/m³ — the contract floor for dining seats.
- 40–50 kg/m³ — hotels, long-dwell lounges, bars.
- 55+ kg/m³ — heavy-duty and 24-hour use.
Compression set is the real killer
Compression set measures how much thickness foam permanently loses after sustained load. A low-density foam at 12% compression set is flat within a year of daily service; a 35 kg/m³ foam at under 8% holds its shape for years.
Ask for both numbers. A quote that gives density but not compression set is hiding the figure that matters.
Specifying seat build
- Dining, 45–90 minute dwell: 30–35 kg/m³, 40–50 mm.
- Lounge and bar: 40 kg/m³ with a softer top layer.
- High-turnover: 35 kg/m³ plus a wrap that keeps moisture out of the core.
Pair the foam with an abrasion-rated cover — see Martindale ratings.
