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Mattress firmness is the single biggest factor in whether a mattress actually suits you, more than material, brand, or price. Get it right and you wake up supported; get it wrong and even an expensive mattress can leave you with a stiff back or restless nights. Here's how to work out what mattress firmness you need.
Mattress firmness is usually described on a 1 to 10 scale, where 1 is the softest possible surface and 10 is the firmest. In practice, almost no mattress sold falls below 2 or above 9, most fall between 3 and 8. A useful way to think about the scale: 3 to 4 is soft, 5 to 6 is medium, 6 to 7 is medium-firm, and 8 and above is firm. The number isn't a guarantee of comfort by itself, it's a starting point that needs to be matched against how you actually sleep.
Side sleepers generally need a softer surface (soft to medium) to cushion the shoulder and hip, the two points carrying the most weight in this position. A mattress that's too firm for a side sleeper creates pressure points at these joints, which is the most common cause of a numb arm or sore hip on waking.
Back sleepers usually do best on medium to medium-firm. This range supports the natural curve of the lower spine without letting the hips sink too far, which is what causes lower back strain in a mattress that's too soft for this position.
Front sleepers typically need firm support. Without it, the midsection sinks lower than the chest and hips, pulling the lower spine out of alignment for hours at a time, which is why front sleepers report the most discomfort on mattresses designed for the average side or back sleeper.
Body weight shifts the whole scale. A heavier sleeper compresses a given mattress further than a lighter sleeper would, so the same "medium" mattress can feel soft under one person and correctly supportive under another. As a general guide, heavier sleepers (over roughly 90kg) often need to choose one step firmer than their sleep position alone would suggest, while lighter sleepers (under roughly 60kg) can often go one step softer.
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Shop MattressesThis is one of the most common mattress buying problems, and there's no single firmness that fully satisfies two very different preferences. The most reliable solutions are a mattress built with different firmness zones, two single mattresses joined on a shared base so each side can be chosen independently, or, as a compromise, meeting in the middle at medium-firm, which tends to be the firmness range fewest sleepers actively dislike.
Our mattress range is available across the full firmness spectrum, Soft, Medium-Soft, Medium, Medium-Firm, Firm, and Extra-Firm, in pocket spring, memory foam, and hybrid builds. If you're unsure where to start, medium-firm is the safest general choice, and every mattress carries a 12-month to 5-year guarantee depending on the model, so you're covered while you settle in.