The density of a mattress is a measure of the mass of the foam or other materials that compose it per unit volume. It is expressed in kilograms per cubic meter (kg/m³). The density of a mattress is an important characteristic because it can affect the quality and comfort of sleep.

In general, the higher the density of a mattress, the firmer and more durable it will be. This means that the mattress will be less likely to deform or compress over time, which can contribute to better sleep quality in the long run. Mattresses with a higher density can also be heavier and more expensive than mattresses with a lower density.

On the other hand, mattresses with a lower density may be softer and more comfortable. However, they can also compress more quickly and lose their firmness over time, which can reduce sleep quality and require more frequent replacement.

The density of a mattress is also related to the quality of the foam it is made of. High-density foams are generally more resilient and durable, while low-density foams can be softer but less durable.

It is important to note that mattress density should not be confused with firmness. The firmness of a mattress is determined by the force required to compress the foam and is measured in ILD (Indention Load Deflection). A denser foam can be both firm and soft, while a less dense foam can be both soft and saggy.

In short, the density of a mattress is a measure of the mass of the foam or other materials that compose it per unit volume, expressed in kilograms per cubic meter (kg/m³). It can affect the firmness, comfort, and durability of the mattress. Mattresses with a higher density are generally firmer and more durable, while mattresses with a lower density are generally softer but less durable. It is important to find a balance between density and firmness to choose a mattress that suits your sleeping style and preferences.