Memory Foam Mattresses: The Facts

Mattress Construction

Memory foam mattresses are made from polyurethane and consist of two main layers. The bottom (core) layer provides the structural support. On top sits a softer memory foam layer, typically 5 to 15 cm thick.

The foam is made up of billions of tiny air-filled cells. When you lie down, your body heat causes these cells to gradually release air, allowing the foam to mould to your shape. When you get up, the cells refill with air and the mattress returns to its original form. This is where the name "memory foam" comes from.

The density of the foam determines how it performs. Higher-density foams (above 50 kg/m³) contour more closely and last longer. Lower-density foams are cheaper but wear out faster.

Advantages

• Pressure relief: memory foam distributes your weight evenly, reducing strain on pressure points like the shoulders and hips. This makes it a popular choice for side sleepers and people with joint pain.
• Hypoallergenic: the dense foam structure is resistant to dust mites and has anti-microbial properties, making it suitable for allergy and asthma sufferers.
• Motion isolation: when one person moves, the foam absorbs the movement rather than transferring it across the bed. This is a significant advantage for couples.

Disadvantages

• Temperature sensitivity: memory foam retains body heat, which can make the bed feel uncomfortably warm for some sleepers. The foam is also firmer at lower room temperatures and softer when warm.
• Initial smell: new memory foam mattresses have a noticeable chemical odour that can take a few days to a couple of weeks to fade.
• Adjustment period: it can take several weeks to get used to the feel of memory foam if you are switching from a sprung mattress.
• Reduced mobility: the contouring effect can make it harder to roll over or change position during the night.

What To Look For

The two most important factors when choosing a memory foam mattress are density and firmness.

• Density ranges from around 30 to 80 kg/m³. Higher density means better contouring and longer life, but also more heat retention and a higher price.
• Firmness depends on the thickness of the comfort layer. A thinner top layer produces a firmer feel because your body sinks less into the foam.

If you are unsure which firmness suits your sleeping position, our firmness guide walks through the options. For a comparison with pocket sprung construction, see our memory foam vs pocket sprung guide.

To compare prices on memory foam mattresses across UK retailers, check our mattress listings page.