Latex Mattress Firmness Ratings – What are ILD’s and What do they mean?

What Are ILD Firmness Ratings on a Latex Mattress?

ILD firmness ratings are the standard measurement used to describe how firm or soft a piece of latex feels. ILD stands for Indentation Load Deflection, and understanding this number is the key to choosing the right latex mattress configuration for your body type and sleeping position. Whether you are building a custom latex mattress or selecting a topper, ILD ratings tell you exactly what to expect from each layer.

How ILD Is Measured

ILD is measured by pressing a circular disc into a piece of latex foam and recording how many pounds of force are needed to compress it by 25% of its original thickness. ILD is the pounds of force required to compress a latex layer by 25%. The higher the value, the firmer the latex; Sleeping Organic’s current customer options are shown below.

Sleeping Organic’s current latex choices run from X-Soft Talalay 14–19 through X-Firm 44. Within those options, the lower numbers feel softer and the higher numbers feel firmer.

ILD is measured at multiple points across the latex surface, typically at the center and edges, and averaged. This is important to know because the edges of a latex layer may feel slightly softer than the center due to the manufacturing process.

ILD Firmness Scale for Latex Mattresses

Best ILD Ratings by Sleeping Position

Side Sleepers: ILD 14–19 or 19–22 (Comfort Layers)

Side sleepers need softer latex in their top comfort layers to allow the shoulders and hips to sink in and relieve pressure. For current Sleeping Organic options, X-Soft Talalay 14–19 or Soft 19–22 provides enough cushion to prevent pressure point pain without letting the body sink too deep. The bottom support layers should be firmer, typically ILD 30–32, 37–40, or 44, to maintain spinal alignment.

Talalay latex in the 14–19 or 19–22 ILD range works especially well for side sleeper comfort layers because its more uniform cell structure provides consistent, gentle cushioning. Learn more about the best latex mattress for side sleepers and latex toppers for side sleepers.

Back Sleepers: ILD 37–40 or 44 (Comfort Layers)

Back sleepers generally prefer a firmer sleeping surface that supports the natural curvature of the spine without allowing the hips to sink too far. Firm 37–40 or X-Firm 44 in the top comfort layer provides the firm, supportive feel some back sleepers need. Dunlop latex works particularly well for this sleeping position.

Read more about the best latex mattress for back sleepers and latex toppers for back sleepers.

Stomach Sleepers: ILD 30–32 (Comfort Layers)

Stomach sleepers need a firm enough surface to prevent the pelvis from sinking, which would cause lower back strain. However, they also benefit from a slightly softer second layer (ILD 19–22) beneath the firm top to provide some body contouring without excessive sinkage. This layered approach gives stomach sleepers the flat, supportive surface they need with just enough cushion.

Explore the best latex mattress for stomach sleepers and latex toppers for stomach sleepers.

Combination Sleepers: ILD 30–32 (Comfort Layers)

If you switch between positions throughout the night, a Medium 30–32 ILD comfort layer offers the best compromise. This provides adequate pressure relief for side sleeping while still offering enough support for back and stomach positions. Pair the Medium comfort layer with Firm 37–40 or X-Firm 44 Dunlop support layers on the bottom for a versatile, all-position mattress.

How ILD Differs Between Dunlop and Talalay Latex

Both Dunlop and Talalay latex use the same ILD scale, but the same ILD number can feel slightly different between the two processes. Talalay latex at ILD 30–32 will feel lighter and bouncier than Dunlop latex at ILD 30–32, which feels denser and more substantial. This is because the Talalay process creates a more uniform, open cell structure, while Dunlop produces a denser, heavier foam.

As a general guideline, Talalay latex works best for comfort layers where you want a responsive, pressure-relieving feel. Dunlop latex excels as support layers where density and durability matter most.

How ILD Affects Mattress Durability

Higher ILD latex is denser, which means it contains more rubber per cubic inch. This makes it more resistant to wear, compression, and body impressions over time. A 44 ILD Dunlop latex support layer will last longer than a 19–22 ILD Talalay comfort layer simply because there is more material to withstand years of nightly use.

This is one reason why custom latex mattresses from Sleeping Organic use firmer, denser Dunlop on the bottom and softer Talalay or Dunlop on top. The durable support layers provide a long-lasting foundation, while the comfort layers can be swapped if they soften over many years of use.

ILD Is for Latex, Not Memory Foam

ILD is specifically used to rate latex foam firmness. Memory foam mattresses use a different measurement system based on density (measured in pounds per cubic foot). The two scales are not directly comparable, so do not try to match ILD numbers from a latex mattress to density ratings from a memory foam mattress.

Choosing the Right ILD for Your Custom Mattress

When building a natural latex mattress, you select the ILD for each individual layer. Here is a practical approach:

1. Determine your primary sleeping position and use the ILD recommendations above for your top comfort layer.
2. Choose a firmer ILD for your bottom support layer(s), typically ILD 37–40 or 44 in Dunlop latex.
3. Consider your body weight. Heavier sleepers (over 200 lbs) generally need higher ILD comfort layers to avoid sinking too deep. Lighter sleepers (under 130 lbs) often prefer lower ILD for adequate pressure relief.
4. If you share a bed, consider a split configuration so each person can select their ideal ILD independently.

Pair your mattress with a natural shredded latex pillow for consistent head and neck support that complements your chosen firmness.

Frequently Asked Questions

What does ILD stand for on a latex mattress?

ILD stands for Indentation Load Deflection. It measures the firmness of latex foam by recording how many pounds of force are needed to compress a piece of latex by 25% of its thickness. Higher ILD means firmer latex, lower ILD means softer.

What ILD is best for side sleepers?

Side sleepers typically do best with comfort layers in the 14–19 or 19–22 ILD range. This provides enough softness for the shoulders and hips to sink in and relieve pressure. The bottom support layers should be firmer, around ILD 30–32, 37–40, or 44, to maintain proper spinal alignment.

What is the firmest ILD available for latex?

The firmest ILD commonly available for mattress latex is 44. Latex at this ILD is very firm and dense, best suited for bottom support layers or sleepers who prefer an exceptionally firm surface. Most people find ILD 44 too firm for a comfort layer unless they are a heavier sleeper or strong back sleeper.

Does a higher ILD mean a better latex mattress?

Not necessarily. Higher ILD means firmer and more durable latex, but the “best” ILD depends entirely on your sleeping position, body weight, and comfort preferences. A side sleeper on a 44 ILD comfort layer would likely experience pressure point pain, while a back sleeper on a 14–19 ILD layer might not get enough support.

Can I change the ILD of my latex mattress after purchase?

With a custom latex mattress from Sleeping Organic, yes. The modular layer design allows you to swap individual layers for different ILD ratings without replacing the entire mattress. This is one of the biggest advantages of a customizable latex mattress system.

Is ILD the same as mattress firmness?

ILD measures the firmness of individual latex layers, not the overall feel of a finished mattress. The perceived firmness of a complete mattress depends on the ILD of each layer, the number of layers, the mattress cover, and the foundation underneath. Two mattresses with identical top-layer ILD can feel different based on their support layer configuration.