If you have looked at a latex spec sheet, you have likely seen ILD listed alongside thickness and density. For buyers new to sourcing latex, it is worth understanding exactly what this number means, since it is the single most useful figure for predicting how a finished mattress, topper, or pillow will actually feel.
What ILD Means
ILD stands for Indentation Load Deflection. It is a standardized test that measures how much force, in pounds, is required to compress a foam sample by 25 percent of its thickness using a flat, round indenter of a specified size. The result is expressed as a number: the higher the ILD, the more force it takes to compress the foam, and the firmer it feels. A lower ILD means the foam compresses more easily under less force, producing a softer feel.
Because the test method is standardized, ILD gives buyers a consistent way to compare firmness across different suppliers and different batches, rather than relying on subjective descriptions like “medium” or “plush,” which can mean different things from one manufacturer to the next.
Why ILD Matters More Than Density
Density, often shown as a D-rating, is also listed on many spec sheets, and it is sometimes assumed to indicate firmness. In practice, density measures the weight of the foam per unit of volume, which relates more to durability and material quantity than to how the foam feels under pressure. Two pieces of latex can share a similar density but have noticeably different ILD ratings, and vice versa. For predicting feel, ILD is the number to prioritize, particularly for the US market, where buyers and end customers are accustomed to firmness being described this way.
Our Firmness Scale
We supply natural latex across five standard firmness levels, each tied to a specific ILD range:
| Feel | ILD Range |
|---|---|
| Extra Soft | 12–20 |
| Soft | 18–23 |
| Medium | 24–29 |
| Firm | 30–37 |
| Extra Firm | 38–45 |
Note that the ranges overlap slightly at the edges, which is normal in foam manufacturing and reflects the reality that firmness sits on a continuous scale rather than in strictly separate bands. When you specify a feel by name, we can confirm the exact ILD target for your order.
Matching ILD to Your Product
Choosing the right ILD depends on where the latex sits in your construction and what feel you are targeting for the finished product:
- Comfort layers and pillow fills are frequently specified in the Extra Soft to Medium range, since these layers sit closest to the body and are meant to cushion rather than support the full structure.
- Support cores are typically specified in the Medium to Extra Firm range, since this layer carries the structural load of the mattress and needs enough resistance to maintain shape and support over time.
- Toppers can be specified across nearly the full range depending on whether the goal is a plush overlay or a firmer, more supportive addition to an existing mattress.
- Multi-zone cores, such as five-zone or seven-zone constructions, use different ILD targets across sections of the same core, typically softer under the shoulders and firmer under the hips and lower back, to match support to body weight distribution.
If you are building a new product line and are not sure where to start, a useful approach is to request samples across two or three adjacent firmness levels and test them side by side, rather than guessing from a spec sheet alone.
A Practical Note on Testing
ILD figures can shift slightly with temperature, humidity, and the time elapsed since manufacture, since foam behaves somewhat differently in a cold warehouse than in a temperature-controlled lab. When comparing suppliers, it is reasonable to ask when and how their ILD figures were tested, and to request current data rather than relying on general published averages.
Ready to Specify Your Order?
We supply natural latex across every ILD in the scale above, in the thicknesses and sizes your build requires, including custom specifications on request. If you already know your target ILD, we can quote directly against it. If you are still narrowing it down, our team can help you match a firmness level to your product goals.
The best way to judge firmness is to feel it yourself. Request a Free Sample across the ILD range you are considering before you finalize your specification.