---
title: "Foam Density (kg/m³)"
description: "What foam density in kg/m³ means on a mattress spec, why it is not firmness, and how it relates to durability."
url: "https://bedguide.co.uk/glossary/foam-density/"
category: "glossary"
primary_entity: "foam density"
date_published: 2026-10-21
date_modified: 2026-10-21
---

# Foam Density (kg/m³)

> Foam density is the mass of foam in one cubic metre, measured in kg/m³. It is not the same as firmness. Higher density usually means more material in the same space, which often resists permanent dips better. Soft high-density foam and firm low-density foam both exist. Read density with hardness and layer depth.

**Definition.** Foam density is how much foam mass fits in one cubic metre, in kg/m³. It is not the same as how firm the foam feels.

Also called: foam density, kg/m3, density rating.

Hardness is a separate measure, often given as ILD or IFD. A foam can be dense
and soft, or light and firm.

Compare density between foams of the same type. Memory foam and reflex foam are
not graded on the same scale.

Full guide: [foam density explained](/mattresses/foam-density-explained).

---

Source: https://bedguide.co.uk/glossary/foam-density/ · BedGuide — independent UK bed guide; paid links are labelled (see /how-we-make-money/). Facts checked against official sources where possible; see https://bedguide.co.uk/editorial-policy. Report an error: https://bedguide.co.uk/corrections.