Memory Foam Density - Common Issues

The importance and role of memory foam density in a memory foam mattress sometimes isn't made very clear, so let me explain the basics:

Memory foam density, usually expressed as KG/m³ (kilograms per cubic meter) is the clearest indication of the quality of the memory foam and the production cost as higher density foams physically have more material in them.

When you see the foam density of a mattress, for example 50KG/m³ it means simple that one cubic metre of the memory foamfoam (a square block 1m x 1m x 1m) will weigh 50 kilograms.

Common Retailer Issues

Having worked in online mattress retail for over five years, I came across a number of issues first hand that I want to make consumers aware of.

3. Density ratings. relation to firmness and ILD / IFD ratings

Some retailers advertise the memory foam density in relationship to the firmness of the mattress which is wrong. Memory foam density is in no way an indicator of the firmness of a mattress as low density foams can be firm, and high density foams can be soft.

Some brands describe products by saying 'density rated as',which I think is misleading as density isn't rated - it is a simple measurement of weight. Using the term 'rated' makes it sound like a subjective value rather than a fact.

2. Foam density not adjusted for so-called airflow holes or channels

You often see mattresses with so-called airflow holes or channels cut into the foam, like in the pictures below:

Apart from my own opinion regarding the effectiveness of these so-called cooling channels (have you ever seen these designs tested or proven?) here is my other problem with them:
If you cut holes in memory foam and remove material from the foam, you are effectively lowering the density of that layer of foam. So where you see a mattress in this style listed with the foam density, you have to ask did they adjust the density advertised to take into the account the material they removed? If a mattress uses 50KG/m³ foam and 15% of the material is removed to make these holes, it effectively reduces the density to 42.5KG/m³.

I have the same issue with the egg box or cratered style of foam:

In previous years (at a different memory foam company) manufacturers would promote this style of foam as a way to make products cheaper, rather than better. If you take our Nytex Pro 700 mattress for example - it features a 7cm top layer of 50KG/m3 memory foam (without holes or channels or any other nonsense).

If we were to use the cratered foam style, we could cut two 7cm layers from one 10cm thick piece of memory foam. Imagine the style pictured above with a 3cm solid lower part, and 4cm in the bumps and craters. The opposite half of the layer would use the opposite 4cm in bumps and craters, with another 3cm solid base.

Doing this would cut the physical cost of the memory foam by about 30% while also lowering the effective density by 30%. Again, ask your retailer how their density was measure before you buy a topper or mattress with this style of foam - or better yet - buy a Nytex memory foam mattress from us (we admit to being biased on this point).

1. Brands or retailer lie, or don't know what the density is

Some brands and retailers might lie about the density they use in the memory foam because they know that most customers won't actually check the density (or don't know how to check) after they've bought the product.

I know this for a number of reasons.

The first clue is usually in the price of the product, so if the specification looks too good to be true... you know the rest. Genuinely high-spec products should carry a higher price tag for obvious reasons.

The second indicator can be applied to toppers where the weight of the item is listed. Using some fairly simple maths (and a free density calculator) you can check the weight of the item matches up to the density listed as follows:

Density in KG/m³ = Mass (weight in KG) divided by the volume in metres (length x width x height)

(Just remember to calculate the volume in metres, so a double mattress length of 190cm is 1.9 metres.)

This formula only applies to toppers as mattresses are usually made up of a number of components or layers. Also bear in mind a topper will weigh more with a cover on.

And if you think it's impossible that some brands or retailers don't know what goes into their products, then you haven't seen the problems reported by the BBC on the Fake Britain Special: Furniture Inferno.

About Nytex Memory Foam

Avoid the pitfalls above by buying from us on our website or from

All the specifications of our products are clearly listed, and all of our products are made in the UK by our NBF approved manufacturing partner (with over 30 years in the business).

Nytex offers trusted, genuine products and all with a 60 night trial, so you can't go wrong.

Jeremy - Founder

Nytex Memory Foam­­®

Dare To Do Better Ltd

(Thanks go to for use of image of the feet on the bed)

Jeremy Lawson
Jeremy Lawson