Let's start here. There isn't one. Certainly some mattresses are better than others, but what works for you might not work for someone else. I'm sure you've had the experience of sleeping rather well on a poor quality mattress in a hotel or motel, and you may have also had the rather unpleasant experience of sleeping poorly on a very expensive mattress in your own home. So rather than ask "what's the best mattress?" let's instead consider the more useful question - "how do you find the right mattress for you?" And to find that mattress, you need to consider two things. First, what do you find comfortable? And second, is the mattress you're considering made of quality materials?
So how do I find something that's comfortable? The easiest way to find a comfortable mattress is to go into a local store and try out a few beds. I would strongly recommend finding a local manufacturer rather than a big name store, as local manufacturers typically use more durable materials and at better prices. You might find that you like the classic feel of a traditional innerspring mattress, or the slightly more conforming feel of a pocketed coil system. You might also enjoy the feel of an all foam bed. If nothing (or everything) feels comfortable to you, then I'd advise you to consider what you've slept well on in the past. This might give you a clue as to what works well for your body. I generally prefer an alternating coil innerspring (a slightly more conforming traditional innerspring) or a pocketed coil mattress. I've slept well on some foam mattresses, but I generally find these to be too warm. Once you have an idea of what you like, then it's time to evaluate each mattress for its quality.
And how do I evaluate a mattress for its quality? Mattress quality is primarily determined by the quality of its two main components: the quality of the support system and the quality of the comfort layers. The support system for most mattresses is typically a spring system or a layer of dense foam (typically polyfoam or latex). Other more exotic support systems do exist (such as wool, water, or air), but these are much less common. Comfort layers are typically much softer foams (either polyfoam, memory foam, or latex) or much softer coil systems (called microcoils). Some other comfort layers include gel matrixes, wool, or cotton batting. So for simplicity's sake let's break this discussion into two parts: foam quality and spring quality.
What are quality foams? This is the easiest part of evaluating a mattress and is usually what people take away from the Mattress Underground. Generally, quality is determined by the density of the foam as measured by pounds per cubic foot (lb/pcf) as denser foams are more durable and retain their "showroom feel" for longer. For ease of understanding I'll break these down into three categories.
- Polyfoam: Or polyurethane foam. This is the most common comfort material and has a "classic" foam feel. My own polyfoam quality metric is as follows: 1.0lb/pcf or lower is very low quality; 1.2lb/pcf is low quality; 1.5lb/pcf is a medium quality; 1.8lb/pcf is high quality; and 2.0lb/pcf or higher is very high quality. However, most mattress companies (and sales people) will use "high quality" to mean just about anything, so make sure you ask for the true specifications. An inch or so of low quality foam is generally permissible (and typically found in the quilt layer), but anything more than that and it's a riskier proposition and prone to premature "flattening" or loss of comfort. If you're looking at polyfoam as a support system then you'll want at least a 1.8lb/pcf foam, though 2.0lb/pcf foam or greater is better if you're a heavier individual.
- Memory foam: Or viscoelastic foam. This is quite comfortable, but can have issues with heat retention. Like with polyfoam, lower density layers are typically lower quality. However, with memory foam a lower density foam can also mean that it's slightly cooler, as less dense materials have more air and thereby airflow. Further, there are some new lower density memory foam variants on the market (HyPURgel, Serene Foam, CopperFlex) that are reportedly durable despite low densities. But generally, 3.0lb/pcf or less is low quality; 4.0lb/pcf is a medium quality; and 5.0lb/pcf or higher is high quality. Tempurpedic formerly used 5.0lb/pcf (or even 5.3lb/pcf) foams exclusively, but now they're experimenting with some less dense foams. I should also state that with many (though not all) memory foams, a higher density can also mean a firmer feel.
- Latex foam: Pretty much durable across the board regardless of density, with the proviso that very very soft latex (about 18 ILD or less) can be less durable for persons with heavier body weights. There are also reported issues with synthetic vs organic latex, but I don't have firsthand experience there. I've never seen latex wear out to any significant degree. There are even posts online about folks using latex beds for 40 years!