What Is Foam Density in a Mattress?

Foam density in a mattress is the mass of foam material per unit volume, measured in kilograms per cubic metre (kg/m³) in Australia. It's a durability and quality indicator, not a firmness measure; two foams with the same density can feel completely different in firmness because firmness (measured by ILD, Indentation Load Deflection) is a separate property. Higher density generally means longer lifespan and better support retention, but also higher cost. Below we cover what density actually measures, why it isn't the same as firmness, how to compare density ranges, and how it applies to memory foam specifically.

Key Takeaways

• Foam density is measured in kg/m³ (kilograms per cubic metre) in Australia and indicates how much foam material is packed into a given volume

• Foam density is not the same as firmness: two mattresses of the same density can feel very different, and two of the same firmness can have very different densities

• Higher density generally means longer lifespan: standard-density (28 to 40 kg/m³) foams last 5 to 7 years; high-density (40 to 50 kg/m³) foams last 8 to 10 years

• Higher density costs more and closed-cell foams can retain heat; open-cell foams like our Kloudcell® balance density with better airflow

• Our Koala mattress range is made with Kloudcell®, a durable, high-density open-cell foam engineered to hold its shape and comfort over years of use, with the Koala Luxe featuring 7 targeted high-density support zones

• Look at both density and firmness ratings when comparing mattresses, plus the manufacturer's stated warranty period as a real-world durability signal

What Foam Density Actually Measures

Foam density measures the mass of foam material per unit volume, expressed in kilograms per cubic metre (kg/m³) in Australia. Higher density means more foam material packed into the same physical space, which typically translates to longer lifespan and better support retention over years of use. A 40 kg/m³ foam has twice the material of a 20 kg/m³ foam of the same physical size.

Understanding the density measurement:

• kg/m³ (kilograms per cubic metre) is the standard Australian and metric density unit

• US convention: lb/ft³ (pounds per cubic foot); rough conversion: 1 lb/ft³ ≈ 16 kg/m³, so a 2 lb/ft³ US foam is roughly a 32 kg/m³ AU foam

• Density directly correlates with material cost: higher density uses more raw foam to make the same physical size mattress

• Density is measured on the raw foam material, not the mattress as a whole; a mattress can combine multiple foam densities across different layers

Typical foam density ranges for mattresses in Australia:

• Low density: below 28 kg/m³

• Standard/mid density: 28 to 40 kg/m³

• High density: 40 to 50 kg/m³

• Ultra-high density: 50 kg/m³ and above

For memory foam specifically, density typically runs higher (50 to 80 kg/m³ is common in quality memory foam) because the foam is engineered denser to deliver the characteristic contouring feel.

Foam Density Is Not the Same as Firmness

Foam density measures how much foam material is in a given volume; firmness measures how much force it takes to compress the foam. They're independent properties, so two foams can have the same density but feel completely different in firmness, and two same-firmness foams can have very different densities. This is the single most common foam-density misconception in the mattress market.

The two measurements at a glance:

• Density = kg/m³: material mass per volume (durability indicator)

• Firmness = ILD (Indentation Load Deflection) or IFD: force required to compress foam by a set percentage (feel indicator)

Two example scenarios that show they're independent:

• Two 40 kg/m³ foams can have very different ILD values: one soft (60 N to compress 25%), one firm (200 N to compress 25%)

• Two same-firmness (medium-firm) foams can have very different densities: one 30 kg/m³ (will soften over 3 to 4 years), one 50 kg/m³ (holds firmness for 10+ years)

The buying implication: firmness rating tells you how the mattress will feel; density tells you how long it will feel that way. A "medium-firm" mattress at 25 kg/m³ won't stay medium-firm for long; the same feel at 45 kg/m³ will hold up for years. Check both when comparing.

High vs Low Density Foam at a Glance

Foam density falls into four broad ranges in the Australian mattress market, each with a corresponding lifespan expectation, price tier, and best-fit use case. Density on its own doesn't decide overall mattress quality, but it strongly predicts how long the mattress will hold its support.

For everyday adult primary-mattress use, high density (40 to 50 kg/m³) is the sweet spot where durability, support retention and cost balance out for most Australian buyers. Below 28 kg/m³ compresses too quickly for daily use; above 50 kg/m³ delivers premium longevity but at premium cost.

Does Higher Foam Density Mean a Better Mattress?

Higher foam density generally means a better mattress in terms of durability and support retention, but not automatically in terms of overall quality or comfort. You want density high enough to last the mattress's intended lifespan, paired with the right firmness for your body and sleep style, plus construction features (zoning, cooling, ticking, edge support) that suit your needs.

Reasons higher density is usually better:

• Longer lifespan: high-density foams retain support 3 to 5 years longer than low-density

• Better edge support: denser foam holds structural integrity at the mattress perimeter

• Reduced body impressions ("sag") over time because dense foam resists compression fatigue

• Better motion isolation: denser foam absorbs partner movement more effectively

• More consistent support across the mattress life; the feel you buy is closer to the feel you'll get in year 5

Reasons higher density isn't always the right answer:

• Heat retention in dense closed-cell foams; open-cell foams (like our Kloudcell®) address this by keeping the density benefit without the heat build-up

• Weight: higher-density mattresses are heavier, harder to rotate, harder to move

• Cost: high-density foams cost more; sometimes better overall value sits in mid-density paired with quality construction elsewhere (zoning, cooling ticking, comfort layers)

• Feel preferences: some sleepers prefer the softer feel of lower-density foam; density doesn't determine feel

The right question isn't "how high is the density?" It's "is the density high enough for how long I want the mattress to last, given how it will be used?"

How Foam Density Applies to Memory Foam Mattresses

Memory foam density typically runs higher than standard polyurethane foam density because memory foam is engineered denser to deliver its characteristic contouring feel. Quality memory foam sits at 50 to 70 kg/m³; budget memory foam below 50 kg/m³ typically shows body impressions within 2 to 3 years of daily use.

Memory foam density ranges specifically:

• Below 50 kg/m³: budget memory foam. Body impressions form within 2 to 3 years of daily use; not recommended for primary-mattress use

• 50 to 60 kg/m³: mid-market memory foam. 5 to 7 year lifespan for daily use

• 60 to 80 kg/m³: premium memory foam. 8 to 10 year lifespan with deep contouring feel

• 80 kg/m³ and above: specialist memory foam. 10+ years, deepest contouring, highest cost

The trade-off with high-density memory foam:

• Advantage: deeper contouring, longer lifespan, slower body impression formation

• Disadvantage in traditional closed-cell memory foam: heat retention. The denser the foam, the more heat it can trap unless the foam is engineered with cooling technology

• Disadvantage generally: heavier weight and higher cost

Our Kloudcell® is made with durable, high-density foam engineered as an open-cell structure, so you get the durability benefit of high density with the airflow of open-cell construction. That combination delivers the pressure-relief contouring associated with memory foam without the heat retention dense closed-cell memory foam is known for, and it's why the Koala Luxe pairs its Copper Kloudcell® comfort layer with seven targeted high-density support zones. Every foam layer in our range is CertiPUR-US® certified.

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Explore Our Kloudcell® Mattress Range Built for Long-Lasting Comfort

Our Koala mattress range is made with Kloudcell®, a durable, high-density open-cell foam engineered by our sleep team to hold its shape and comfort over years of use with better airflow than traditional dense closed-cell memory foam. All 5 models feature CertiPUR-US® certified foam, Zero Disturbance® technology, our 120-night trial, and 10-year warranty. Explore the range:

• Koala Mattress: the flippable Firm/Medium-Firm original, 25 cm total height with 7 cm Kloudcell® (40% more than SE), zip-off topper with carbon-zero TENCEL™ Lyocell ticking, and 3-zone charcoal marble dyed support layer.

• Koala Plus Mattress: flippable Medium-Firm/Medium, 28 cm total height with 8 cm Kloudcell® (60% more), Cooling Gel Kloudcell® flippable comfort layer, reversible summer/winter topper, and 5-zone support with bamboo charcoal edge support.

• Koala Luxe Mattress: our plushest option, 31 cm total height with 9 cm Kloudcell® (80% more), 3 cm zip-off quilted topper with Australian Cashmere blend and Phase Change Material, Copper Kloudcell® comfort layer, and 7 targeted high-density support zones.

• Koala SE Mattress: our entry model, Medium firmness, 23 cm total height with 5 cm Kloudcell® and TENCEL™ Lyocell breathable cover.

Browse our full premium mattress range for all firmness levels and price points.

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