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Density vs firmness — the conversation that goes wrong
Density (kg/m³) is the weight of foam material per cubic metre. It is a measure of how much foam is in a given block. Firmness (IFD or ILD) is the force required to compress the foam by 25% of its thickness — a measure of how stiff it feels under load.
The mistake we see weekly in incoming RFQs is buyers asking for "32 density firm" without specifying the IFD. A 32 kg/m³ foam can be tuned soft (IFD 28), medium (IFD 36) or firm (IFD 48) without changing the density at all. Density predicts durability; IFD predicts feel. Both numbers are needed.
Foam density chart
The quick reference — grade, typical density, feel and how long it lasts. Detailed notes on each family follow below.
| Foam type | Density (kg/m³) | Feel | Typical use | Service life |
|---|---|---|---|---|
| PU 24 | 24 | Soft | Decorative cushions, soft toys | 2–3 yrs |
| PU 28 | 28 | Soft–medium | Entry guest bedding, occasional seating | 3–4 yrs |
| PU 32 | 32 | Medium | Mid-tier seating | 5–6 yrs |
| HR 32 | 32 | Medium-firm, springy | Standard sofa seat cushion | 6–8 yrs |
| HR 36 | 36 | Firm, resilient | Heavy-use & hospitality seating | 8–10 yrs |
| HR 40 | 40 | Firm, premium | Executive & vehicle seating | 10+ yrs |
| Bonded 80 | 80 | Firm | Mattress core (light–medium) | 8–10 yrs |
| Bonded 100 | 100 | Very firm | Mattress core (medium–heavy), back support | 10–12 yrs |
| Bonded 120 | 120 | Extra firm | Institutional mattresses, gym mats | 12+ yrs |
| Memory 40 | 40 | Soft contour (closed-cell) | Mid-tier mattress comfort layer | Warmer sleep |
| Memory 50 | 50 | Soft contour (open-cell) | Premium mattress comfort layer | Breathable |
| Memory 55 gel | 55 | Soft, cool | Premium mattresses, pressure-relief pillows | Coolest, most stable |
Density predicts durability; firmness (IFD) predicts feel. Two foams at the same density can feel soft or firm depending on how they are tuned.
PU foam — flexible polyurethane
General-purpose polyurethane foam. Most cost-effective grade. Used where cost matters more than long-term cycle life.
24 kg/m³ PU: Decorative cushions, soft-toy fillings, low-cycle headboards. Service life under regular seating use: 2–3 years.
28 kg/m³ PU: Entry-tier guest bedding, occasional-use seating. Service life: 3–4 years.
32 kg/m³ PU: Mid-tier seating with manageable cycle load. Service life: 5–6 years.
Note: For furniture seating and mattress cores, we will recommend HR foam or bonded foam over PU at the same density — the cost difference is usually 10–15% but the service life roughly doubles.
HR foam — high-resilience polyurethane
Bouncier, more responsive, better fatigue performance under cyclic load. The default choice for seating cushions.
32 kg/m³ HR: Standard sofa seat cushion. Service life 6–8 years.
36 kg/m³ HR: Heavy-use seating, hospitality banquettes, premium home sofas. Service life 8–10 years.
40 kg/m³ HR: Premium executive seating, long-haul commercial vehicle seats. Service life 10+ years.
Bonded foam — re-bonded polyurethane
Made by re-bonding chipped foam under heat and pressure. Distinctively firm, excellent edge support, very long service life. Workhorse of mattress support cores and high-cycle institutional bedding.
80 kg/m³ bonded: Mattress support core for light–medium sleepers. Service life 8–10 years.
100 kg/m³ bonded: Mattress support for medium–heavy sleepers, back-pain mattresses. Service life 10–12 years.
120 kg/m³ bonded: Hostel and hospital mattresses, gym mats, edge-reinforcement layers. Service life 12+ years.
Memory foam — viscoelastic
Temperature-sensitive viscoelastic foam. Slow recovery, contour-fitting, excellent pressure relief. Used as a comfort layer over a firmer core — never as the support core itself.
40 kg/m³ standard: Mid-tier mattress comfort layers. Closed-cell, may sleep warm.
50 kg/m³ open-cell: Premium mattresses, breathable, well-suited to Indian climate.
55 kg/m³ gel-infused: Premium mattresses, pressure-relief pillows. Coolest variant, longest IFD stability.
How to specify foam in an RFQ
A complete foam spec has six pieces. If you share all six, your supplier can quote accurately and dispatch samples without follow-up questions:
1. Grade family: PU, HR, bonded or memory.
2. Density: kg/m³.
3. IFD or ILD target: approximate value or a soft/medium/firm preference.
4. Slab dimensions: length × width × thickness in mm or inches, with tolerances.
5. Finishing: cut, profiled, ground, fabric-quilted, fire-retardant, anti-static, etc.
6. Monthly volume: in number of slabs, m³ or kg.
The more detail you give, the tighter the first quote will be. Use our RFQ form and we will respond within 24 hours.
Frequently asked questions
What foam density is good for a mattress?
For the support core, look for bonded foam at 80–100 kg/m³. For comfort layers, HR foam at 40 kg/m³ or memory foam at 50 kg/m³ and above. Higher density resists sagging and extends the mattress's life.
Is higher foam density always better?
Not always. Higher density lasts longer but costs more and feels firmer. Match density to the use: 32 kg/m³ HR foam is fine for a home sofa seat, while a mattress core benefits from 80 kg/m³ or higher bonded foam. Density predicts durability; firmness predicts feel.
What density of foam should I use for a sofa seat cushion?
For home daily-use sofas, 32 kg/m³ HR foam tuned to medium-firm IFD (30–38) gives 6–8 years of service life. For heavy-use or hospitality seating, step up to 36–40 kg/m³ HR.
Is 24 kg/m³ PU foam ever acceptable?
Yes, for low-cycle applications — decorative cushions, occasional-use headboards, soft-toy fillings, packaging cushioning. For furniture seating or mattress cores, it is not economic; the service life is too short to justify the small cost saving.
How is bonded foam different from regular PU foam?
Bonded foam is made by re-bonding chipped foam pieces under heat and pressure into a dense block. It is significantly firmer than regular PU at the same density and offers much longer service life. It is the workhorse of mattress support cores.
Should I specify density or IFD in my purchase order?
Both. Density predicts durability; IFD predicts feel. A purchase order that only specifies one leaves room for the supplier to ship something that meets the letter but not the intent of the spec.
How fast can a North India foam supplier dispatch samples?
For standard density grades held in inventory, 48–72 hours from RFQ. For cut-to-spec custom grades, 5–7 working days from order confirmation. Khanna (Punjab) is under 12 hours by truck to most North India furniture clusters.
Got a furniture-foam spec ready?
Send the spec via our RFQ form — we’ll respond within 24 hours with price, lead time and a sample plan. Sample dispatch in 48–72 hours for standard grades.
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