How to measure mattress firmness and support
The feeling of a mattress tested for just a few minutes can be deceptive. To measure mattress firmness effectively, it is not enough to ask if it is hard or soft: you need to understand how it reacts to weight, how well it supports different areas of the body, and whether it keeps the spine properly aligned throughout the night.
An apparently rigid model may sag too much under a robust body. Conversely, a mattress perceived as welcoming can offer high load-bearing capacity thanks to its internal structure. The right choice comes from the meeting of firmness, materials, posture, and personal physical characteristics.
Firmness, load-bearing capacity, and comfort: they are not the same thing
In common parlance, any feeling of support is often called "firmness." From a technical point of view, however, it is useful to distinguish between three concepts.
Firmness describes the initial resistance the mattress offers to pressure. It is what you perceive when you lie down: a soft, medium, or firm embrace. Load-bearing capacity (or support), on the other hand, is the ability of the structure to hold a specific load without collapsing and without losing correct support over time. Comfort is the end result: it depends not only on firmness but also on elasticity, pressure distribution, breathability, and how the materials respond to movement.
This is why two mattresses classified as "medium-firm" can be very different. Memory Foam may slowly cradle the shoulders and pelvis, while a pocket-sprung mattress may appear more responsive and supportive while offering comparable load-bearing capacity. The commercial rating alone does not tell the whole story of the sleep experience.
How mattress firmness is measured in the factory
Firmness is evaluated through compression tests performed on materials and the finished product. In foam mattresses, such as memory foam, polyurethane, or latex, a value often considered is the ILD (Indentation Load Deflection), which is the load required to compress the material by a defined percentage. In general, a higher ILD indicates a foam that is more resistant to compression.
This data is useful, but it is not enough for making a decision. The ILD concerns a specific layer and does not fully describe the behavior of a mattress composed of multiple materials. A model may have a soft surface layer and a very supportive load-bearing layer: it feels welcoming at first contact, but maintains stability under the body's weight.
Density also matters, especially in foams. A higher density does not automatically mean a harder surface, but it often indicates a more consistent and durable structure. This is an important element for those looking for a mattress suitable for intensive daily use, a larger body type, or support that remains stable over time.
In pocket-sprung mattresses, the feeling depends on the number, shape, and gauge of the springs, as well as the padding layers. In latex, thickness, density, and the type of processing influence the result. For this reason, comparing only words like "firm," "orthopedic," or "ergonomic" is not enough: the entire sleep system must be evaluated.
Firmness scales are for guidance only
Many manufacturers use a scale from 1 to 10 or labels like soft, medium, medium-firm, and firm. These are practical references, not universal standards. A "7 out of 10" may be perceived differently by a 55 kg person versus a 105 kg person, or by someone who sleeps primarily on their side versus someone who sleeps on their back.
This is why firmness should never be chosen as an absolute number. The right question is: does this level of support keep my body properly aligned without creating localized pressure?
Measuring mattress firmness on your own body
At home, you do not need professional tools to evaluate if a mattress is suitable. You need careful observation, performed under conditions as similar as possible to those of real sleep. The most significant test lasts more than a few minutes: the body needs time to relax its muscles and joints.
When lying in a supine position (on the back), the pelvis should not sink deeper than the shoulders. If it does, the lumbar area loses support and tension may increase upon waking. If, conversely, the mattress remains too high and flat under the back, without adapting at all to the natural curves, it can leave a sensation of pressure and stiffness.
When sleeping on your side, your shoulder and hip must be able to sink enough to keep the spine horizontal. A mattress that is too firm can compress the shoulder and arm, causing tingling or frequent waking. One that is too soft can cause the pelvis to sink too much, creating an unnatural lateral curvature.
In a prone position (on the stomach), evaluation requires even more attention. This posture tends to accentuate the lumbar arch, so in many cases, it requires a more stable surface, but not necessarily one that is extremely hard. If the pelvis sinks, the back works all night in an unfavorable position.
A practical signal is how you feel when you wake up. Lumbar pain that diminishes after moving around, sore shoulders, a stiff neck, or the need to change position repeatedly can indicate that the support needs to be reviewed. These are not medical diagnoses, because pillows, bed bases, and daily habits also come into play, but they deserve attention.
Body weight: the factor that changes perception
The same mattress does not work the same way for everyone. A light person exerts less pressure and may perceive as firm a model that feels balanced to a heavier person. Conversely, those weighing over 90-100 kg often need higher load-bearing capacity—not to sleep on a hard surface, but to avoid excessive sinking and a rapid loss of performance.
The solution is not to automatically choose the firmest mattress available. Support that is too firm can concentrate pressure on contact points and reduce comfort. It is more effective to look for a structure with an adequate load-bearing base and a surface layer capable of distributing weight. High-density memory foam, pocket springs with differentiated support, and some latex models can respond very differently to the same requirement.
Height and weight distribution also count. A body with broad shoulders and narrower hips may have different needs than a build that concentrates the load in the pelvic area. This is why a choice based only on weight, while useful, does not replace a complete ergonomic evaluation.
Posture, back pain, and differentiated zones
Those who suffer from back pain often tend to look for a firm mattress. It is an understandable belief, but it oversimplifies things. An excessively hard surface does not support better by definition: it may prevent the shoulders and pelvis from settling correctly, leaving the spine out of alignment.
For many people, the most balanced choice is medium or medium-firm support with good adaptability. Mattresses with differentiated zones are designed specifically to offer different responses to the shoulders, lumbar area, and legs. Their effectiveness, however, depends on the quality of the structure and the match between the mattress zones and the person's height.
If the pain is persistent, acute, or associated with diagnosed medical conditions, a mattress does not replace the advice of a specialist. It can, however, help create a more favorable rest environment, especially when chosen together with an adequate pillow and a bed base in good condition.
The bed base modifies perceived firmness
A mattress never works alone. A bed base that is too yielding makes even a supportive model feel softer; a rigid or worn-out base can alter weight distribution and worsen comfort. Slats should be intact, well-spaced, and compatible with the type of mattress chosen.
This aspect is decisive with memory foam and latex, materials that need a base capable of promoting aeration and uniform support. Before blaming the mattress for every problem, it is worth checking the condition of the bed base and verifying that it does not have dips or damaged slats.
For a couple, firmness can be customized
When two people have very different weights, postures, or preferences, a single degree of firmness can become an unsatisfying compromise. A significant difference in build can make the same mattress feel too soft to one person and too firm to the other.
In these cases, a solution with differentiated load-bearing capacity on the two sides can offer a concrete benefit. Furthermore, in double mattresses with pocket springs, movement independence helps limit the transmission of nightly shifts. It does not solve every need, but it improves rest when one partner moves often or gets up at different times.
The most reliable choice does not stem from the idea of an "absolutely perfect" mattress, but from a precise evaluation of the body that will use it. A guided path like the one proposed by JoyShop Materassi helps transform generic terms like soft or firm into a concrete choice, based on weight, posture, perceived heat, and support needs.
Sleeping well means feeling the mattress present where it is needed and almost imperceptible elsewhere: a support that accompanies the body, not a surface against which the body must adapt.
