Memory Foam Mattresses: Finding the Right Firmness and Density

Choosing a new memory foam mattress is a tricky thing.

There’s just so much you have to consider—especially if you’ve never gone for foam before.

The decision you make on your mattress today could have an impact on your sleep quality for years and years to come, but it can sometimes feel like you don’t even know where to begin!

When shopping for memory foam in particular, two particularly important factors you want to get right are density and firmness.

These two variables can have a huge impact on your sleep quality and quantity, so it really pays off to get these things right.

So, here it is—the complete guide to choosing the right density and firmness in your memory foam mattress.

Firmness vs Density

Although firmness and density are often fairly closely linked, they’re definitely not identical.

Density is an objective measurement of pounds per cubic foot.

Firmness, on the other hand, is a subjective measure of how soft or hard a mattress feels when you lie down.

Denser mattresses do tend to be a little firmer, but that’s not necessarily guaranteed.

What’s the Best Firmness Level?

A couple in a showroom perches on top of a mattress, feeling its firmnessAlthough the ideal mattress firmness level varies quite a bit from person to person, about 80% of all people are satisfied with something between a medium-soft and a medium-firm mattress (or somewhere between a 5 and a 7 on the 1 to 10 mattress firmness scale).

It’s difficult to say the exact degree of firmness that will work best for you.

You can read some general tips in our full article here, and SleepLikeTheDead.com offers a few handy charts you can check out here.

If you’re still having trouble figuring out what firmness you need, though, it’s often best to go down to a brick-and-mortar store just to try out a couple different levels and see what you like.

Indentation Force Deflection

Now, even after you decide on the firmness level you think you’ll need, your job still isn’t quite over.

That’s because the boundaries between things like “medium” and “medium-firm” tend to get a little fuzzy when you start looking at different mattress companies’ products.

It’s an entirely subjective measurement, remember, so what feels just right to one person might feel too hard or soft to you.

Thankfully, though, memory foam mattresses actually do have a standard test for measuring firmness.

It’s called Indentation Force Deflection (IFD), and it’s standard across the entire industry.

IDF measures the number of pounds of force it takes for a 50 square-inch circle to compress a patch of memory foam by 25%.

The lower the score, the lower the firmness.

(Note: some mattress companies may refer to Indentation Load Deflection (ILD), instead of Indentation Force Deflection. These terms are interchangeable, and the measurements are the same—ILD is just based on the metric system, rather than the standard system.)

What’s a Good IFD?

Generally, you want your memory foam mattress to have an IFD somewhere between 10 and 16.

An IFD of 10 to 12 will be on the softer side, with a good amount of sinkage.

12 to 14 is medium (which is probably what you want), while 14 to 16 is medium-firm.

Below 10 and you start getting into extremely soft mattresses, while about 16 and you start getting extremely hard.

Limitations of IFD

Although IFD is useful, it’s important to realize that it does have some limitations.

First of all, it only measures the firmness of the viscoelastic memory foam in your mattress—not any of the other layers’ firmness.

Second of all, it can vary quite a bit in response to things like humidity and heat.

And finally, not all foam mattress companies actually provide the IFD of their websites.

They do have that number somewhere, though—so if you really want to find out a product’s IFD, you should be able to call up a business and find out.

What is the Best Density Level?

Density, on the other hand, is a little bit more concrete in the mattress industry.

There’s no wiggle room here—all memory foam mattresses have a density, which you can find by simply dividing the volume of the mattress by the mass.

You can think of foam density as the weight of a single cubit foot of the material.

Again, there is no single answer to the question, “What is the best density level in a memory foam mattress?”, since everything is based on personal preference.

However, there are some things you can generally expect from low- and high-density foams.

Low-Density Foam Pros and Cons

Low-density foams typically weigh less than three pounds per cubic foot.

They tend to feel softer (although this isn’t always true), and since they take less material than high-density foams, they’re often cheaper, too.

According to SleepLikeTheDead.com, they tend to retain less heat than higher-density foams, meaning you’re less likely to sleep hot, and they also have a greater responsiveness than their counterparts—that is, it takes the foam less time to adjust to the weight and figure of your body, which is a plus if you tend to shift positions a lot in the night.

Low-density foam also tends to have reduced temperature sensitivity, which means you’re less likely to experience the “sinking” feeling some people dislike in memory foam mattresses.

This also makes them better for sex in many people’s eyes.

They also tend to have less of a smell when new.

That said, though, low-density foams tend to lose out on a lot of the benefits a lot of people are looking for in memory foam mattresses.

Since they conform less to the shape of your body, they offer less back pain relief and tend to provide less of the “floating” feeling a lot of people love in memory foam mattresses.

They also tend to be less durable than higher-density foams,

Higher-Density Foam Pros and Cons

Woman lying on a cloud floatingMedium-density foams, on the other hand, weigh three to five pounds per cubic foot, while high-density foams weight five pounds or more.

The higher the density, the more a foam mattress tends to take on the unique characteristics of memory foam.

You get more responsiveness, heatiness, contouring, back pain relief, sinkage, and that special floating sensation.

They tend to be worse for sex (though that’s of course subjective), they tend to smell more, and they’re always heavier, meaning they’re more difficult to move.

High-density foams also tend to be more expensive, although there are quite a few exceptions to this.

Your Personal Needs

Obviously, the final judge of your ideal memory foam density is always going to be your personal needs. 

That’s what you’re buying a new mattress for, after all—so you can get a more comfortable night’s sleep.

There’s no comprehensive guide that can tell you whether low-density or high-density foam is going to be a better fit for you, and there are some things you just have to judge for yourself.

That said, though, one other factor you want to take into account when selecting a memory foam density is your weight.

Heavier people sink into materials more readily than lighter people, so the heavier you are, the denser a memory foam you’re likely to want.

If you don’t go dense enough, you’ll likely feel like you’re drowning in foam.

You go too dense, and you won’t get the kind of give and support you need.

The Final Verdict on Density

In addition to your personal wants and needs, there are also a couple more objective measurements you can have a look at when making the final decision on memory foam denseness.

Here on Mattress-Guides.net, we’ve actually compiled a huge amount of data on mattress reviews from across the internet to determine the absolute highest-quality mattresses on the market today.

Our absolute highest-rated memory foam mattress—the Amerisleep AS3—uses medium-density foam.

A lot of other top-rated mattresses—Nolah, Nectar, and Bear, for instance—use high-density foam, and in fact, you’d be pretty hard-pressed to find a top-rated mattress with a low density (you can see this for yourself on our ultimate mattress-buying guide)!

That said, though, this doesn’t necessarily mean that high-density foam always means you’ll be satisfied.

For instance, almost all of our top-rated memory foam mattresses have some kind of additional technology to ensure they sleep cool.

You’re not going to find these kinds of perks in a lower-quality high-density memory foam—and you’ll probably be disappointed.

Remember that you can’t trust any one factor to bring you a satisfactory mattress experience.

Density and firmness are just two considerations you should have when researching your next buy!

Conclusion

With all this information, you should now be feeling much more confident about what variety of memory foam mattress is going to work best for you.

This puts you one step closer to finding the ultimate mattress experience!

It might seem tedious or time-consuming right now, but always remember that this research will pay off in the end.

Your sleep is worth investing in.

Just be sure to take your time now, and you can rest easy for years and years to come!

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