Thinking about buying a mattress, but wondering about all the specs?
There are upwards of 100 brands selling memory foam mattresses online with different densities, and they’re all offering different features. The only thing they seem to have in common is the promise of the best sleep of your life. But they can’t all be right, can they?
Today’s beds are better than ever, with advanced materials, quality control and a rapid pace of innovation. But what feels like the perfect mattress for one person could feel like a sinkhole to someone else. At the end of the day, our individual preferences are as different as the vast array of bed-in-a-box brands.
That’s why we created this guide for memory foam density. Of all the different features and specs to sort through as you’re comparing brands, the foam density is incredibly important and related to durability, quality, and individual comfort.
What are Foam Density Ratings?
We all learned about density during school, but we probably never thought about how it applies to a bed.
As a quick review, density is a measurement of how heavy it is compared to its size. A truckload of feathers, for example, will weigh less than a truck full of steel. That’s because feathers are less dense than steel.
For you visual learners, it’s represented by the equation: Density = Mass/Volume
Most things have density measurements or ratings, including memory foam, which is sometimes referred to as viscoelastic foam. Foam’s density is measured in pounds per cubic foot (PCF).
At the low end of the spectrum, a cubic foot of memory foam will have a rating of 1.5, meaning it weighs 1.5 pounds per cubic square foot. The densest varieties have a rating of 8.0 or 8 pounds per cubic square foot.
By looking at the density of the material when evaluating different brands you’ll know a lot about how durable the bed is as well as how soft or firm it might feel. Armed with this knowledge, it will help you rule out or hone in on different levels that will adequately suit your needs. By looking at this one factor and knowing what’s best for you, you’ll be better equipped to choose a bed that you love.
How Foam Density is Measured
To measure foam density, the manufacturer will take the total weight of the foam layer and divide it by its total volume. For example, if you have a piece of foam weighing 100 pounds and its volume is 25 pounds per cubic foot, you’ll divide 100 by 25 to calculate the density. In this case, the foam’s density would be 4 PCF.
Memory Foam Densities
Memory foam densities vary depending on the particular model. Density ratings can impact the material’s durability and overall performance.
A low foam density is rated at a 3 or less. The lower the number, the less foam that’s used in production. This translates to a less expensive bed as well as a softer one. However, it also means you shouldn’t expect the product to have a long lifespan.
These beds can still be ideal for guest bedrooms, since they won’t be used as often, making durability less of a factor, and the same goes for RV and camper mattresses. They could also work well for children who are light and won’t put substantial weight on the surface, which would normally cause it to sag over time.
Memory Foam Densities
Measurements of 4 to 5 pounds per cubic foot are classified as medium-density. This range is what we call the Goldilocks of mattresses. Most people rate them as not too soft, not too hard, but just right.
Unless you’re looking for an exceptionally firm surface or you’re a heavier individual weighing more than 250 pounds, you’ll probably be happy with a product with a medium rating.
What is high-density foam? When you see a rating of 6 cubic feet or higher, you’re in the high-density range. These beds are the firmest and most expensive.
However, these mattresses should last the longest, so they could be a smart buy for people who want to keep their bed for a long time. Their firmness level also makes them ideal for those with back pain or injuries because of the advanced support.
If you choose a high-density foam bed, keep in mind that it might seem extra firm when you first sleep on it, especially if you’re a lightweight or average-size sleeper. It can take some time for the surface to contour to your body, so be patient for the first few nights.
What Does the Density Affect?
Density can affect many factors that are important to consumers. Understanding these factors can help make a more informed decision when shopping for your new bed.
The most significant predictor of how long a mattress will last is its density rating. Lower numbers have less material, meaning that they break down more quickly and will begin to sag sooner.
Before dismissing a mattress with a low number as subpar, you may also want to look at the quality of the foam. Some are designed better than others, so even though this measurement does give you some indication of how durable the bed is, it’s not the only factor.
The official firmness measurement for foam is called Indentation Load Deflection (ILD). Denser foams are also likely to have a higher ILD rating. Manufacturers measure ILD by taking a foam sample and compressing it to 25 percent of its total thickness. The thicker the material remains, the higher the ILD. Firmness is important because it can help you pinpoint beds that are supportive enough for your sleep style and body type. A firmer, more supportive mattress will ensure proper spine alignment, preventing back pain and fostering more comfortable sleep.
Need more info? Check out our complete mattress firmness guide.
As density levels rise, so does the price. This is primarily due to the amount of material that’s used to make something the same size. A high-density bed has more foam in it than a lower one, which elevates the cost.
Often, you get what you pay for, so before adding a budget bed to your cart and celebrating your savings, consider that what you’re buying might not be as comfortable or last as long.
Check Out Our Guide: Highest Rated Budget Mattresses
Memory foam is famous for contouring your body’s curves and giving you a gentle hug while you sleep. This level of comfort is what makes viscoelastic mattresses the most highly rated in terms of customer satisfaction.
Again, the higher the density, the less contouring you can expect, although all memory foam beds, regardless of their number, will respond to your body heat and weight to provide some give.
In years past, viscoelastic was criticized for sleeping hot because its contouring effects meant that air didn’t circulate around the body. Those days are long gone, thankfully. New technologies have emerged that allow the viscoelastic material to stay cool in the bed and circulate air.
Read More: Best Cooling Mattresses for Hot Sleepers
If you’ve seen the television commercials of the person pressing their hand into foam, then you’ve noticed that there’s usually a lasting handprint on the surface. The longer the imprint stays is a measure of response time.
Brands with lower densities respond faster because they have more air inside, which allows the material to bounce back. A high-density brand will keep the imprint of your weight longer, which also makes it a bit more of a challenge to roll over when it’s time to get up or switch positions.
You already know that the denser the material, the heavier it is. Therefore, a high-density viscoelastic mattress will weigh more than one that has a lower number associated with it.
If you plan on moving to a new house soon or you have a lot of stairs to climb, you might want a lighter bed for that reason. However, if you need a denser bed, you can inquire about white glove services. White glove delivery is when the mattress company will place your new bed in the room where you want it and assemble it for you.
One of the primary reasons many people love memory foam is because it’s so successful at melting away pressure. That being said, memory foams with a higher density rating will typically contour the sleeper closer than lower density versions. Therefore, if you want a memory foam bed that’s going to give more personalized contouring and pressure relief, a medium to high-density option would be best.
Sleep quality is a matter of personal preference. Some people prefer a soft sleeping surface with extra cushioning. Others want a firmer surface that doesn’t cause them to feel like they’re sinking into their bed.
Some other factors to consider are how much you weigh. A 120-pound person will perceive the firmness of a bed differently than someone who weighs 200 pounds. That’s because the lighter person won’t sink into the surface as deeply since they’re not exerting as much pressure. Therefore, heavier individuals may want to seek out higher density materials, whereas lightweight people may prefer a lower density rating.
Looking for more information? Here you can read more about sleep quality.
What Foam Density is Best for Different Sleeping Positions
Your sleep position can play a significant role in selecting the ideal foam density. Plus, matching the right density to your sleep style increases your chances of more comfortable slumber.
Side sleepers tend to get the most out of memory foam because pressure easily accumulates in this posture. The foam is able to hug the sleeper’s curves, causing uncomfortable pressure to melt away. Side sleepers will likely benefit most from a low to medium density. The slightly lower densities mean the foam has more give to better accommodate the hip and shoulder areas.
Find Out More: Best Mattress for Side Sleepers
Back sleepers also benefit from memory foam’s ability to soothe pressure points, particularly for the shoulders in this position. Most people who rest on their back will find a medium-density the most comfortable, though there may be variations for those who weigh less or more. For example, a lightweight back sleeper may enjoy the softness of the low-density foam, while a heavier back sleeper would likely benefit more from the high-density version.
Find Out More: Best Mattress for Back Sleepers
For stomach sleepers, the main priority is keeping the body in alignment since the midsection is prone to sinking in if it’s not well-supported. Most stomach sleepers find that they’re more comfortable on firmer beds that keep the midsection level and prevent added pressure on the lower back. For this reason, these sleepers should only consider high-density foam.
Find Out More: Best Mattress for Stomach Sleepers
If you're a combination sleeper, that means you’re rotating among different sleep positions throughout the night. These sleepers typically need foams that are dense enough to support them in multiple positions, but ones that also have some give for better responsiveness, which allows them to reposition easier. In this case, a medium-density should be best.
Find Out More: Best Mattress for Combination Sleepers
Frequently Asked Questions
Does high-density foam mean it’s a firm mattress?
Even though high-density ratings are often associated with firmer surfaces, that’s not the only variable that affects how a mattress feels.
Another important number to look at is the indentation load deflection (ILD). This number indicates how much force is required to put a one-inch dent in the material. ILD is tested with a giant machine that presses down a piece of foam and tracks the power exerted. The higher the ILD number, the firmer the bed.
What thickness and density level is best for mattress toppers?
The answer to this question depends on the reason you’re buying a mattress topper. If your bed is too firm, and you’re looking for a way to soften it, then a 2 to 3-inch thick topper with a low to medium density will provide the most amount of comfort.
If your bed isn’t supportive enough or you’re trying to extend the life of your mattress, look for a topper that’s 3 to 4 inches thick and has a higher density.
What density level is good for side sleepers?
Side sleepers tend to need a softer mattress that cushions the body’s curves. The reason is that when people sleep on their side, the weight of their shoulders and hips presses deeply into the surface. A typically recommended density is approximately 4.0, but there’s a wide range that many will find acceptable.
The landscape of bed-in-a-box brands can be confusing, and the industry has introduced a lot of new jargon that most people aren’t familiar with. Hopefully, this guide on memory foam density will help you better understand each brand’s product descriptions, so that you can choose the bed that will provide you with years of restful sleep.