Mattress Density Guide

Mattress density guide: Comfort at your fingertips.
Mattress Density Guide
Tom Greenspan
December 21, 2022

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How does the density of your mattress impact your life? For most people buying a new mattress has two fundamental questions and objectives, is the mattress soft or firm? But what makes a mattress soft or firm? Is it solely the construction of the mattress, or is it the materials used in the mattress? Most folks look at memory foam as a new type of mattress material, but the truth is memory foam has been around since the moon landing way back in 1969, and there has not been a lot of innovation to memory foam in all those decades.

Due to its viscoelastic qualities, memory foam can expand and adapt to pressure and heat. A memory foam mattress conforms to the individual contour of each sleeper as a result, even as they move around during the night. In this article, we explore mattress densities and what relationship it has to your sleep and comfort. We answer frequently asked questions to help guide you through the process of understanding how mattress density will impact your comfort and sleep.

Let's jump in.

How is the density of mattress foam measured?

For example, memory density and other foams are measured in pounds per cubic foot. If you have 2 12 x 12-inch cubes of foam and one cube has a value of 1.0, and the other has a value of 1. 8, the higher value foam has 80% more foam than the foam with the lesser value. The foam with the higher value is also 80% heavier. Ok, so what's the big deal? Well, if you can pack more foam into a 12 x 12-inch cube, it becomes dense and gives more support, and the mattress will be firmer.

Mattress manufacturers use the density of the foam to dictate if the mattress is soft or firm, and not just one foam is used in the mattress. Below is s a standard chart that manufacturers and retailers use to define the firmness of the mattress and comfort level you may be seeking:

Memory foam mattress density

Some manufacturers classify foams with pounds per cubic foot of four or less as low density, while others don't classify a foam as high density unless it has pounds per cubic foot of at least 5.5. These broad ranges offer you a rough idea of what to anticipate in terms of how the memory foam will feel and perform. There are multiple layers of memory foam in memory foam mattresses, though. Each layer of memory foam in them is composed of several layers, several of which have various densities. Some designs even combine layers of poly-foam and memory foam.

Each layer's interaction with the layers around it will impact how the mattress supports the body, responds to movement, and absorbs body heat. The density of each layer should be compared to one another to give you a general idea of the mattress's long-term performance. It is crucial to understand the dynamics of memory foam and other foams that are used in the mattress, so you purchase the correct mattress for your body shape and weight.

Memory foam densities defined?

Low density

Less than three pounds of foam are contained in each square foot of low-density memory foam. Compared to high-density memory foams, they are relatively quick to regain their original form and are lightweight. While some people adore the way memory foam cradles them, others feel trapped by the body indentations. Low-density memory foam's rapid response time frequently feels better for combination or restless sleepers.

Historically memory foam has a history of trapping heat and making users uncomfortable while they sleep. Because they are not as tightly packed as high-density memory foams, low-density memory foams are more breathable and allow more heat and air to escape.  Low-density foams are also less expensive since they require fewer raw materials, resulting in lower costs overall. Numerous low-density memory foam layers can be found in entry-level or inexpensive mattresses.

However, there are several drawbacks to using low-density memory foam. There is less material to support the body when there is less foam per square foot. Low-density foams might not support some sleepers, such as those who experience back pain or have heavier bodies. Sadly, low-density foams typically have a lower level of resilience. In other words, they begin to degrade more quickly than their high-density counterparts. 

Low-density foam loses its ability to assume its original shape over time quickly. Low-density foams typically last five years or fewer.

Who should buy low-density foam mattresses?

There is a market for the low-density foam mattress, and it's worth considering if you meet the following criteria:

  • You tend to move around in your sleep and prefer side sleeping.
  • If you hate the way memory foam heats through the night, the lower-density foam will sleep cooler.
  • If you are lightweight and are 130 lbs or less, this mattress could be the perfect choice for you.


  • Breathability, keeping the mattress sleeping cooler.
  • Responsive, the mattress is very responsive to movement.
  • Cost efficient compared to higher density memory foams.


  • Durability, the less dense foams degrade faster.
  • Less support for those over 130 lbs.

Medium density

Foams with a medium density have a per cubic foot of three to five. Of course, they fall somewhere between the heavier high-density memory foams and the lighter low-density memory foams. The additional foam per square foot offers the body more support than low-density foam. To give the mattress a cozier feel, there is also extra foam that directly touches the body.

Low-density memory foam is more breathable than medium-density memory foam. However, medium-density memory foam does allow more air to move around than high-density foam.  Medium-density foams are more durable than low-density foams due to the additional foam per square foot. Medium-density foams typically last six to eight years.

Who should buy medium-density foam mattresses?

There is a market for the medium-density foam mattress, and it's worth considering if you meet the following criteria:

  • Those of you who need back and joint support.
  • Active sleepers.
  • Body weight of 130 to 230 lbs.


  • Cost effective when amortized over the expected life of the mattress.
  • Supportive and responsive
  • More comfort and a feeling of being cradled


  • Sleeps warmer than low-density memory foam.
  • Insufficient support for heavier body weights.


A per cubic foot of five or above indicates high-density memory foam. You're more likely to find a memory foam mattress with a per cubic foot of 8.5 or lower. These foams are the densest and heaviest memory foams because they contain the greatest substance. The viscoelastic characteristics of the lower-density foams are still present in all that material. Still, because more material is pressing against and conforming to the body, you will experience more support and tighter contouring.

High-density foams lift and support the spine more, maybe better-accommodating people with back discomfort or heavy sleepers. The strongest foams are those with a high density. Due to the enormous volume of foam, it takes longer for them to degrade. Therefore, they could endure 10 years or longer.

In addition, there is less room for heat to escape due to the densely packed foam. As a result, high-density foams may be too warm for those who quickly become overheated when sleeping.  And the least responsive material is high-density foam. Memory foam leaves an imprint when your hand presses into it and then removes it. That impression or "memory" will last longer in a high-density foam than it would in a low- or medium-density foam.

Who should buy high-density foam mattresses?

There is a market for the high-density foam mattress, and it's worth considering if you meet the following criteria:

  • Sleepers who suffer from back and joint pain.
  • Body weight in excess of 230 lbs
  • Active sleepers.


  • Ideal for aligning the spine and preventing back pain, close to an orthopedic-style mattress.
  • Mattress longevity is the most durable mattress of all memory foam mattresses.
  • Comfortable when the mattress is broken in giving support. Sleep on the mattress and not in it.


  • Cost.
  • Sleeps hot
  • Breathability.

Does density indicate how firm a mattress is?

High-density foam is commonly thought to feel firmer. Although it significantly impacts how a mattress feels, density is not a reliable indicator of firmness.  The ILD, or (Indentation Load Deflection), must be taken into consideration while evaluating hardness. A foam piece measuring 15 by 15 by 4 inches is compressed until it is 25 percent of its original height to determine the ILD. 

The foam is considered to have an ILD of 25 if it takes 25 pounds of pressure to reach the 25 percent threshold. Soft or plush foams generally have an ILD below 19, whereas stiff foams have an ILD around or beyond 50. A medium-feel foam is defined as everything in between.  Low-ILD memory foams are common in the comfort or top layers of mattresses, whether made entirely of memory foam, blended with other types of foam, or hybrids. 

These foams can also be low or medium-density to improve responsiveness, conformability, and breathability. Medium-density foams are frequently used in the comfort layers, but you may also find them in the transition layers of mattresses to provide additional support. However, depending on the model, the density of the transition layer foams may be low, medium, or high.

Many memory foam mattresses have a transition and support core of high-density foam. They can support the spine and provide mattress form and longevity.  The high-density support cores are frequently thought to be quite rigid. This is accurate for certain mattresses. In other cases, the high-density support layer is soft to improve the mattress's cushioning and conformability. It's important to realize that neither density nor ILD is equivalent to hardness. While a low-density foam may feel solid, a high-density foam may feel soft. 

The inverse may also be accurate. It depends on how the foam is made and constructed. In contrast to the ILD, which describes how soft or firm the mattress feels, the density of the foam provides a good indication of the mattress's strength and support.

How does memory foam density affect your sleeping position?


Memory foam's capacity to conform to body shapes frequently works best for side sleepers. Pressure on the shoulders and hips is reduced while the waist's curves are filled.  Because they can conform to the sleeper's contour, memory foams of all densities are suitable for side sleepers. To avoid feeling trapped in a mattress made primarily of high-density memory foam, restless-side sleepers may prefer a mix of foam densities.

Choose a bed that is medium in firmness when looking for the best mattress for side sleepers because these mattresses are made to provide an even balance of comfort and support.

Back sleepers

Finding a mattress is simpler for back sleepers than for some other sleep positions because their spine naturally maintains a neutral position. Back sleepers can choose their preferred level of contouring and cushioning while making decisions. To adequately relieve pressure and pain, you will likely require extra high-density foams if you have back pain.

Stomach sleepers

Due to the additional strain it places on the lower back, it is not advised to sleep on your stomach. Even so, you may wake up feeling sick to your stomach.  High-density foam provides added support for stomach sleepers. Additionally, they often find that firmer mattresses prevent the hips from sinking too far into the mattress, helping them sleep better.

Combo sleepers

alternate between several sleeping positions. They still require high-density foam for support, but they might gain from adding at least one layer of a more responsive low or even medium-density foam to avoid creating a rut that is difficult to move out of.


A new mattress is an investment, so making the correct choice is paramount for long-term sleep and comfort. However, when it comes to density, it's not the only answer to your problems. Not only will selecting the right mattress for your body and sleeping style enable a good night's sleep, but you may be keeping your mattress for many years of delightful sleep and rest.