Buying a new mattress is often seen as a simple task—one that boils down to finding a product that matches the size and price range of your choice. However, when faced with the vast selection available in stores and on websites, it’s easy to feel a little overwhelmed and ask yourself that recurring question: What factors should you consider when choosing the best mattress?
In fact, not only are there several types of mattresses—such as foam, spring, and latex—but consumers also have to navigate concepts that may be unclear to them: firmness, thickness, comfort, softness, and density.
It is this last criterion—density—that we’ve chosen to focus on, offering to guide you toward the best possible choice based on your body type, your expectations, and the impact of a mattress’s density on its comfort, firmness, and lifespan. In other words, how do you choose the right density for your mattress so you can enjoy a sleeping surface that provides you with the best possible sleep?
What is mattress density?
For many people, the density of a mattress—whether it’s made of springs, synthetic foam, memory foam, or natural latex—corresponds to its firmness: a very dense mattress is a very firm mattress, and vice versa.
In reality, however, a mattress’s density is a physical measure that indicates the amount of material used to make the mattress’s foam or latex, regardless of its thickness or size. Mattress density is measured in kg/m³; depending on the manufacturer, you may find the average density of all the mattress layers listed, or information on the density of each individual layer of material inside the mattress.
A mattress’s density therefore affects its weight and its estimated lifespan—based on its durability under daily use, night after night—and also influences its level of support, which depends on the body type and weight of its users, given the same density. It is easy to see that the support provided by the same mattress, with the same density, will differ for a 25-kg child compared to a 90-kg adult.
A mattress’s density is therefore not directly synonymous with firmness. In fact, a foam or latex mattress with a density of 40 kg/m³ may be firmer than one with a density of 50 kg/m³, especially since the overall firmness of a bedding set is also determined by the quality of the box spring paired with the mattress. According to bedding experts, the box spring accounts for one-third of a bed’s quality and comfort, with the remaining two-thirds attributable to the mattress.
The density levels of different types of mattresses
As you will see, the concept of density primarily applies to foam or latex mattresses, since the density of innerspring mattresses is not related to the quantity or quality of the material—these mattresses consist of springs surrounded by air and padding. For spring mattresses—whether pocketed or not—support and firmness are determined by the number of springs present and the firmness of each spring, which is technically and physically very different.
Synthetic Foam Mattresses
You can find polyurethane foam or memory foam mattresses on the market with the following density levels, along with information for each level regarding its typical use and estimated lifespan:
- 20 to 25 kg/m³: poor durability over time; best suited for a guest bed used by a lightweight sleeper or a child;
- 25 to 35 kg/m³: sufficient support and durability for a guest room or for a child under 12 years of age;
- 35 to 45 kg/m³: estimated lifespan of 5 years with daily use as a mattress for one adult;
- 45 kg/m³ and above: 10-year lifespan, which is the recommended maximum before you need to replace your mattress.
Before discussing the density characteristic of natural latex mattresses, we believe it is important to point out what all synthetic foam mattresses have in common: they are manufactured using petrochemicals, which involves the use of chemicals strongly suspected of harming indoor air quality and the health environment in the bedroom.
These environmental and health considerations must be given even greater attention when the mattress is intended for a baby’s or child’s bed.
Natural Latex Mattresses
When you choose a natural latex mattress—regardless of its thickness or dimensions—you’ll enjoy a higher density, ensuring an optimal lifespan of about ten years without any decline in comfort over the course of nights and years.
A well-made natural latex mattress can have a density ranging from 65 to 95 kg/m³, which explains why they are considered the most durable mattresses on the market.
With this level of density, latex mattresses allow people of all body types to find and choose a level of support suited to their body or sleeping position—whether firm, medium-firm, or soft—without needing to use a mattress topper to achieve their preferred level of support.
In addition, when you purchase a mattress labeled "100% natural latex," you are guaranteed to spend your nights in a healthy bed, with a mattress that is naturally breathable, antibacterial, dust-mite-resistant, and free of chemicals—unlike synthetic foam mattresses.
What density should you choose for each body type?
Having a thorough understanding of what mattress density is—regardless of the mattress type—provides concrete mechanical and physical data on the effects of a particular model’s density. This knowledge can then be used to accurately determine the level of support a mattress provides by factoring in its density along with the weight and height of the person who will be sleeping in the bed.
Therefore, for a person weighing between 50 and 70 kg, it is advisable to choose a mattress with a density greater than 65 kg/m³ to ensure proper support for several years. For an adult weighing more than 70 kg, it is best to choose a mattress with a density of at least 75 kg/m³ to ensure a comfortable night’s sleep.
People weighing more than 100 kg should, in theory, choose a mattress with a density greater than 85 kg/m³. Based on the technical specifications regarding density that we have just detailed, it appears that only natural latex mattresses are capable of providing this level of support without sagging or causing pain over time.
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