DNS is a foam's density: the kilograms of material in one cubic metre, so DNS 50 means 50 kg/m³. It says nothing about hardness, which is how strongly the foam resists being compressed. Two foams at the same DNS can feel completely different. Density predicts service life and resistance to permanent deformation; hardness predicts feel under load.
Last updated:
What does DNS literally measure?
DNS is mass divided by volume, expressed in kilograms per cubic metre. A foam labelled DNS 50 is one whose cubic metre weighs 50 kilograms. The unit is usually left off the number, but that is always the quantity being named.
One consequence matters more than the rest: density is independent of the size of the piece. A 3 cm sheet and a 10 cm sheet at the same DNS are equally dense — the thicker one simply contains more material, not denser material.
In rebonded foam the figure is set mechanically, by how much shredded material the press compacts into the mould. In directly blown foam it follows from the chemical formulation. Either way, DNS measures the same thing.
Why are density and hardness not the same thing?
Density answers how much material occupies a given volume. Hardness answers how strongly that material resists being compressed — how far it sinks when you press on it. They are different questions, and the answers are independent of each other.
This is where the most common error in the trade comes from: two foams quoted at the same DNS can feel completely different. Cell structure, the mix of particles used and the amount of binder all change firmness without necessarily changing the kilograms in a cubic metre.
Which figure to ask for depends on what the layer has to do. How many years it will last, and whether it will hollow out under load, is a density question. How it will feel to sit on is a hardness question. No single number answers both.
How do you verify a claimed DNS yourself?
Density is the one specification you can check without a laboratory. Cut a piece of known dimensions, work out its volume in cubic metres, weigh it, and divide the mass in kilograms by the volume. The result is the DNS.
A worked example: a sheet measuring 100 × 100 × 5 cm has a volume of 1 × 1 × 0.05 = 0.05 m³. If DNS 50 is claimed, that sheet should weigh 50 × 0.05 = 2.5 kg. Take a 50 × 50 × 5 cm offcut instead and the volume is 0.0125 m³, so the expected weight is 0.625 kg.
A few details make the measurement trustworthy. Measure the piece uncompressed on a flat surface and cut the edges square — a sloping cut makes the volume read smaller than it is. The larger the sample, the smaller the measuring error, and the more the result averages the block rather than one spot in it. On small samples the resolution of the scale starts to matter too.
If the scale and the declared figure disagree, check first whether the sample came from a part of the block that represents it; edge regions can differ from the middle. If the gap persists across several samples, the declared figure is the thing in question.
Is higher density always better?
No. Density is a design parameter, not a quality score. Raising it means putting more material into the same volume, which makes the part heavier, prices freight by weight rather than by volume, and can leave the layer firmer than the application wanted.
Where higher density genuinely pays is in layers that stay loaded: a mattress base, the fill inside a seat frame, a gym floor, an underlay beneath carpet. What is bought there is not a feel but the ability to hold thickness over years.
For a surface comfort layer, a filling under a cover or single-use packaging cushioning, high density is usually cost with no return. The useful question is never which DNS is highest, but how much load this layer will carry and for how long.
DNS and RG: one quantity, two names
In German-speaking markets the same quantity is called Raumgewicht, abbreviated RG, and it too is given in kilograms per cubic metre. RG 50 and DNS 50 say exactly the same thing: two names, not two measuring systems.
That matters in practice because a German buyer and a Turkish supplier can talk past each other for an entire conversation. The buyer asks for RG, the supplier answers in DNS, and each assumes the other is quoting a different specification. Writing the unit plainly on the offer — kg/m³ — closes the misunderstanding before it opens.
Beyond the name, it is worth settling which material the figure belongs to. A density value always attaches to a specific product, and two materials of different construction carrying the same number will not necessarily behave the same way.
| Property | What it measures | Unit | What it predicts | What it does not tell you |
|---|---|---|---|---|
| Density (DNS / RG) | How much material occupies a given volume | kg/m³ | Load-bearing capacity, resistance to permanent deformation, service life | How firm the foam feels |
| Hardness | Resistance to being compressed | Force at a set compression | Feel under load: soft or firm | How many years the layer will last |
| Thickness | Height of the layer | cm | Overall build height and available travel | How much load the layer can carry |
| Sheet weight | Mass of a single piece | kg | Handling effort and freight load | Density, unless the dimensions are known |
| Compression set | Thickness not recovered once the load is removed | % | Long-term sagging behaviour | How the surface feels on first contact |
Frequently Asked Questions
- Does a higher DNS mean a harder foam?
- No, not necessarily. Density and hardness are independent properties: DNS states kilograms per cubic metre, while hardness states resistance to compression. A high-density material can be soft and a low-density one firm, so hardness has to be asked about separately.
- How do I measure DNS myself?
- Cut a piece of known dimensions, weigh it, and divide the weight in kilograms by the volume in cubic metres. A 100 × 100 × 5 cm sheet has a volume of 0.05 m³, so if it weighs 2.5 kg its density is 50 kg/m³ — DNS 50. The larger the sample, the more reliable the result.
- Are RG 50 and DNS 50 the same thing?
- Yes — both name the same quantity, density in kilograms per cubic metre. RG is the abbreviation used in German-speaking markets and DNS the one common in Turkey. The difference is in the name, not in the measurement.
- What is the difference between DNS 50 and DNS 60?
- The difference is how much material sits in the same volume: DNS 60 holds about a fifth more material per cubic metre than DNS 50, and weighs correspondingly more. That becomes an advantage in layers expected to hold their thickness under continuous load. Which grade suits your build is best settled on the product page or by asking us.
- Should the highest DNS always be chosen?
- No. Density is not a quality score but a parameter chosen to suit the layer's job; more than the application needs only adds weight and cost. Higher density earns its place in base layers that stay under load, and is usually unnecessary in surface comfort layers.
Related products
Used in These Sectors
See the glossary for terms: DNS (Density Grade), Density, Hardness, RG (Raumgewicht), Compression Set, Rebonded Foam, Foam, Polyurethane (PU)
Related guides
Let's Determine the Right Material for Your Project
Our technical team is ready to help you identify the most suitable product and solution for your needs.