Exploring ILD (Latex Firmness)

ILD (indentation load deflection), also called IFD (indentation force deflection) is a measurement of the force required to compress a material by 25% of its thickness. While ILD can be a helpful technical tool for characterizing a sheet or layer of latex, it is often misused or misunderstood.

At Savvy Rest, we recommend customized layer configurations for mattresses based on years of experience, customer interviews and customer feedback, not ILDs.

Now and then, though, we'll field a question about latex ILDs and how they relate to mattress comfort. In order to provide a more complete understanding, we purchased an ILD tester and did some research ourselves.

Here are some of the things we found out from our testing and observations:

The instrument used to measure ILD is a 7.5" diameter circular plate, shaped nothing like a person. So, ILD measurements can't be applied directly to how the foam interacts with your sleeping body.

The ILD rating is valid at 25% compression only. It does not indicate how foam performs when it is compressed more or less than that. For example, some of our Dunlop latex pieces have ILDs similar to our Talalay latex pieces. The Dunlop piece will typically feel firmer, however. That's because when Dunlop is compressed by more than 25%, it "firms up" more than Talalay does.

ILD is only one factor that characterizes how soft or firm a piece of latex is.

The construction of a mattress casing (sometimes called quilting or ticking) also makes a difference in the surface feel by adding cushioning. If a casing is constructed to fit very tightly, the taut surface and compression add to a sensation of firmness. On the other hand, if a casing or quilting is made with lots of fiber or loft and with very stretchable fabric, it can be made to feel very soft (out of the factory).

While it may seem daunting to identify the right mattress firmness for your body, it's very doable. The best option is to try our natural and organic mattresses-with different configurations-at the nearest Savvy Rest dealer. If that's not within reach, call and talk with someone at Savvy Rest about how the mattress will feel. We'll ask you guided questions that will swiftly help you make sense of it.

The bottom line on ILD? Your sleep experience is dependent on much more than the ILD measurements of individual layers-so don't let the numbers keep you up at night.