Sofa foam explained: density, resilience and cushions that keep their shape

Density is the mass of foam in one cubic metre, written as kg/m³. A cubic metre of 35 kg/m³ foam weighs 35 kilograms; the same block at 22 kg/m³ weighs 22. The heavier block simply contains more material and less air.

More material makes a stronger cell structure. Each time you sit down, the tiny cells in the foam are squeezed; each time you stand up, they recover. Denser foam can repeat that cycle many more times before the cell walls break down and the cushion loses height. That is why density is the best single number for predicting how long a seat will stay comfortable, and why it belongs on any serious sofa specification. Our guide to what makes a sofa last puts it alongside the frame, springs and fabric.

No, and this is the most common confusion in sofa shopping. Density describes how much material is in the foam. Firmness, sometimes called hardness, describes how much force it takes to press the foam down, and it is measured separately, often in newtons.

Foam makers can produce a dense foam that feels soft and a light foam that feels firm. A firm, low-density foam can feel supportive on the first day, then soften quickly at home. A soft, high-density foam feels gentle from the start and stays that way. When you compare sofas, ask for both: the density tells you about durability, the firmness or comfort description tells you about feel.

These are general guidelines used across the furniture trade rather than fixed standards, and exact figures vary between suppliers. For a sofa used every day, 35 kg/m³ or more in the seat is a good benchmark. Back cushions carry far less weight, so lighter foam or fibre is a common choice there.

High-resilience foam, often shortened to HR foam, is a polyurethane foam with an irregular, open cell structure. Compared with standard foam of a similar density, it pushes back more the further you sink in, so it feels supportive deep in the seat, and it recovers its shape quickly when you stand up.

In practice, HR foam usually comes in densities of around 35 kg/m³ and above, which is why the two appear together on good specifications. It is the usual core of a quality seat cushion. Layers on top, such as a softer foam or a fibre wrap, then shape the first feel of the seat, from gently soft to plump and cloud-like.

Memory foam is a different material: it moulds slowly to your body and reacts to warmth. It is common in mattresses but rare in sofa seats, because it is slow to recover when people sit and stand all evening.

Most sofas combine them: a supportive foam core for the seat, softer layers for comfort, and fibre or foam and fibre in the back cushions. The softer and looser the top layers, the more plumping the cushions need to look neat. A crisp, tailored sofa usually relies more on foam; a relaxed, slouchy one more on fibre and feather.

You rarely see the foam itself, so ask the right questions and look for the signs:

1. Ask for the seat foam density in kg/m³. A number is a good sign; vague words such as "premium foam" or "luxury comfort" are not.
2. Ask whether it is high-resilience foam, and what is wrapped around it: fibre, a softer foam layer or feather.
3. Press the seat with a flat hand if you can reach the sofa. Good foam pushes back evenly and recovers within a second or two; poor foam feels hollow or slow to spring back.
4. Look at the front edge of the seat. A crisp, full edge that does not slump when you sit on it shows a well-shaped foam block.
5. Check the back cushion filling, since loose fibre needs more plumping than a foam core.

Online, the same questions work: a seller who knows the density and the construction of the cushions has usually chosen them with care. To find out how each of our sofas feels, ask us on WhatsApp.

On every Pufflo sofa you choose the seat comfort, at the same price. Cocoon is very soft: you sink in. Classic is the medium feel most sofas have: you sit on it and get up easily. Both are made with the same care, so a softer feel is simply a matter of taste.

Comfo and Nuage start in Cocoon; Brioche, Snoozo and Doudou start in Classic, and you can choose the other comfort on any of them. To decide which suits you, read soft or firm sofa.

• Plump back cushions every few days, pushing the filling back towards the corners.
• Turn and swap loose seat cushions every week or two, if your sofa has them, so the wear is shared.
• Sit in different places. The favourite corner always wears first.
• Keep cushions out of strong sun. UV light fades fabric and, over time, ages the foam behind it.
• Do not stand or jump on the seat. Concentrated weight crushes foam cells far faster than sitting.

On any sofa, the seat settles gently in the first weeks as the foam and its wrapping adapt to the way you sit, then holds that comfort. A common rule is to look for seat foam of 35 kg/m³ or more, which keeps its shape beautifully with daily use. For a complete routine, see our sofa care routine.