The firmness of a mattress varies greatly depending on the materials used.
For example, memory foam mattresses are often much softer than those made of cold foam, and pocket sprung mattresses are generally much firmer.
That's not to say that all memory foam mattresses are necessarily soft or that all pocket spring mattresses are necessarily firm.
Ultimately, the mattress's exact firmness will depend on the brand, model, composition, and combination of materials within the bed.
You need to consider the type of materials used and how the different layers are positioned.
High-quality mattresses often feature a base layer made of cold foam or polyurethane foam.
These provide additional support and stability.
You also often find a top comfort layer made of memory foam or gel foam.
Many quality mattresses also feature inbuilt contour zones, which help alleviate pain.
These zones regulate and control where your body sinks into the mattress and where it receives more support.
Your shoulders and the pelvic area should generally sink in more deeply than your head and legs.
These contour zones allow for optimal spinal alignment, keeping your body straight and tension-free.
Is memory foam the way to go?
A high-quality soft mattress is often fitted with memory foam.
Memory foam is highly adaptable, offers excellent pressure relief, and provides body-contouring comfort.
It often feels softer than other types of foams, which is great if you're looking for that soft body-hugging comfort.
But, because it adapts so well to the body and gives you that sinking-into-the-mattress feeling, moving around on memory foam can be a little troublesome.
This is why memory foam mattresses aren't recommended for restless sleepers.
Also, memory foam tends to store more body heat than other types of foam.
If you sweat heavily at night or generally don't enjoy a warmer sleep, you should consider materials like latex foam or Geltex instead.
That said, good memory foam mattresses tend to counteract this by adding in cooler foams and cooling mattress covers that allow for greater breathability and increased airflow.
These covers are also often hypoallergenic as well, which is great for people prone to allergies.
You'll also find that memory foam is often used as a top comfort layer or a pillow top on a firmer mattress so that you can enjoy a softer feel while still receiving firm support for a great night's sleep.
The memory imprint of the memory foam gives it that characteristic soft body-hugging comfort.