If you want to know how to choose a mattress in the UK, here is the whole method in three lines. Pick a firmness that keeps your spine straight in the position you sleep in, given your weight. Pick a type, sprung, foam, hybrid or latex, by how it feels and how warm it runs. Then buy from somewhere with a long enough trial that you can return it if you were wrong.
That order matters. Most people start with the type because it is what the adverts talk about, but the type is a matter of preference. Support is what stops you waking with a stiff back, and only a trial tells you whether a mattress supports you. This guide takes each step in turn, then covers UK sizes, budgets and when to replace. It is deliberately brand-agnostic: we do not review mattresses and we do not name products here.
What a mattress is actually for
A mattress has one job: to hold your body so that your spine stays in roughly the same line lying down as it does standing up, all night, without creating pressure points that make you shift. A mattress that is too soft lets your hips sink and your spine sag into a curve. One that is too firm pushes back at the shoulders and hips and leaves the waist unsupported, so you turn more often looking for comfort.
A second job, if you share a bed, is not to transmit every movement across the mattress. A third, increasingly important in warmer UK summers, is to let heat escape rather than store it.
It does not do anything for a busy mind, a noisy street or a bedroom that is too bright. If you are lying awake for those reasons, a new mattress will not help, and the bedroom setup checklist is a cheaper place to start.
In short: Firmness is about support for your body and position. Type is about feel and heat. Trial is about finding out whether you guessed right.
Firmness by sleeping position and weight
Firmness labels (soft, medium, medium-firm, firm) are not standardised, so one brand's medium is another's firm. Use them as a starting point, then test.
Side sleepers need the shoulder and hip to sink in enough that the spine stays level, so they generally want medium or medium-soft. Too firm and the shoulder is pushed up, the neck bends and the arm goes numb. A high, firm pillow completes the picture, as explained in our side sleeper pillow guide.
Back sleepers want medium to medium-firm: enough give for the lower back's curve, enough support that the hips do not sink below the shoulders.
Front sleepers generally do best on medium-firm to firm, to keep the hips from dipping and straining the lower back. Many front sleepers find a thin pillow or none is better.
Combination sleepers who change position should lean towards medium, which compromises least across positions.
Weight changes all of this. A heavier person sinks further into any mattress, so a mattress that feels medium to a lighter person feels soft to them; they usually need a firmer, deeper mattress to get the same support. A lighter person on a firm mattress barely dents it and gets pressure points; they need softer. Couples with a large weight difference sometimes solve this with two single mattresses on a super king base, or with a mattress that has different firmness zones.
Back pain deserves its own note. The limited research on mattress firmness and low back pain, including a Spanish randomised trial published in The Lancet in 2003, suggests medium-firm mattresses may be better than firm ones for people with chronic non-specific low back pain. That runs against the old advice to buy the hardest bed you can. If back pain is persistent, the NHS back pain pages and a GP or physiotherapist come before a shopping trip.
Mattress types explained
Open coil (Bonnell) sprung
A single continuous wire frame of springs, the traditional cheap mattress. Springs move together, so you feel a partner turn, and they wear into a dip in the middle. Fine for a spare room or a child's bed; not a first choice for every night.
Pocket sprung
Each spring sits in its own fabric pocket and moves independently, so the mattress contours to your body and isolates movement better. The number of springs is quoted heavily in marketing; past a reasonable count it says little about quality, and the comfort layers on top matter more. Pocket sprung mattresses are cooler than foam, feel springy, and vary from soft to firm depending on the spring gauge and filling.
Memory foam
Viscoelastic foam that softens with body heat and moulds around you. Excellent at spreading pressure and at isolating movement, which suits couples and people with painful hips or shoulders. It runs warm, can feel like sinking into sand if it is thick and slow, and makes turning over slightly harder. Newer foams with open-cell structures or gel are marketed as cooler; results vary.
Hybrid
Pocket springs with a substantial foam or latex layer on top. The idea is the springiness and airflow of springs with the contouring of foam. Most of the mattress-in-a-box brands sell hybrids. Because the term is loose, check the depth of the foam layer and the type of springs rather than trusting the word.
Latex
Natural or synthetic latex foam is responsive rather than slow, sleeps cooler than memory foam, and lasts a long time. It is heavy, more expensive, and some people dislike its bouncy feel. A good choice for hot sleepers who want a foam feel.
Rolled and boxed mattresses
Not a type but a delivery method. Foam and hybrid mattresses can be compressed and rolled for delivery, which makes home trials practical. They need a day or two to expand and can have a faint smell at first. Sprung mattresses that cannot be rolled are delivered flat.
Trial periods and returns
A mattress takes weeks to judge, because your body needs time to stop expecting the old one. That is why a long home trial is worth more than a few minutes lying on a shop bed with your shoes on. Many UK retailers now offer trials of several weeks to several months on mattresses delivered to your home.
Read the terms before you buy. Check whether the trial has a minimum period before you can return, who collects the mattress and whether there is a fee, whether a mattress protector is required, and whether a returned mattress is refunded in full. Keep the mattress protector on from night one; some retailers refuse returns on stained mattresses.
Give it at least three or four weeks. Judge by how your back feels twenty minutes after getting up, by how often you wake, and by whether you sleep better on it than you did on the old one, not by how it felt on the first night.
UK sizes
Standard UK mattress sizes are: single 90 by 190 cm, small double (sometimes called three-quarter) 120 by 190 cm, double 135 by 190 cm, king 150 by 200 cm, and super king 180 by 200 cm. Small single (75 by 190 cm) and European sizes also exist; EU double and king mattresses are a different shape from UK ones and will not fit a UK frame properly, so if you have a continental or IKEA bed frame, measure it.
Buy the biggest size the room and the budget allow if you share. A standard double gives each person less width than a single bed; a king or super king is the difference between sleeping next to someone and sleeping on top of them. Bed frames, bases and mattresses must all match, and a mattress on a slatted base with wide gaps will sag between the slats.
Budgets, honestly
Price tracks depth, spring count, foam density and brand marketing, not necessarily comfort. A mid-priced mattress that suits your position and weight will beat an expensive one that does not. Spend where it matters: on a mattress you can trial, on a decent protector, and on the right pillow. Avoid buying on sale-price urgency; mattresses are perpetually on offer.
Toppers: the cheaper middle step
If your mattress is sound but slightly too firm, a topper of a few centimetres of foam, latex or fibre can soften the surface without a new mattress. A topper cannot fix a mattress that sags, because it follows the dip, and it adds warmth if it is dense foam. It is a reasonable answer to a firm hotel-style mattress in a rented flat, or to a new mattress that turned out firmer than expected and is past its trial. It is not a substitute for replacing a worn one.
Bases and frames
A mattress is only as supportive as what it lies on. Slatted bases need slats close enough together, usually no more than a few centimetres apart, or a foam mattress will sag into the gaps. Divan bases with a sprung top soften the feel; platform tops firm it up. A mattress that feels wrong on an old base may feel fine on a new one, and a new mattress on a broken base will not last. Check the manufacturer's guidance on suitable bases, since some warranties depend on it.
Heat
If you already wake up hot at night, the mattress is part of the picture. Sprung and latex mattresses let more air through than dense memory foam. Whatever you buy, a breathable protector and cotton or linen bedding make more difference than a 'cooling' label; the bedding and sleep guide covers fabrics and togs.
When to replace a mattress
Most mattresses last around seven to ten years. Signs it is time: a visible dip or roll-together in the middle, springs you can feel through the top, waking stiff on a mattress that felt fine a few years ago, sleeping noticeably better in a hotel or a spare room, or a mattress that creaks, sags or smells. Turning or rotating a mattress as the maker advises extends its life; a good protector keeps it hygienic.
Where to go next
Work out your position and weight, pick a firmness, choose a type you like the feel of, and buy where the trial is long and the terms are clear. Then give it a month. If a new mattress does not change your nights, the problem is probably elsewhere, and the sleep products guides and the environment guides will help you find it.
Frequently asked questions
What firmness of mattress is best for back pain?
The evidence, such as it is, points to medium-firm rather than very firm for people with non-specific low back pain. Firmness labels are not standardised, so try before you commit and judge by whether your spine feels level and your back is no worse in the morning. Persistent back pain is a matter for a GP or physiotherapist.
Is memory foam or pocket sprung better?
Neither is better; they feel different. Pocket sprung feels springier, cooler and more traditional; memory foam moulds closely, isolates a partner's movement and can feel warm. Hybrids combine the two. Choose by feel, temperature and budget, and give any of them a proper trial.
How long does a mattress last?
Around seven to ten years for most, less for cheap foam and more for good latex. Sagging, a visible dip, springs you can feel, or waking stiff on a mattress that felt fine years ago are the signs it is done. A better night's sleep somewhere else is the clearest test.
What are the standard UK mattress sizes?
Single 90 by 190 cm, small double 120 by 190 cm, double 135 by 190 cm, king 150 by 200 cm and super king 180 by 200 cm. UK sizes differ from EU and US ones, so if you have a European bed frame or IKEA bedding, check the frame's measurements before ordering.
Sources and further reading
- NHS: Back pain
- NHS: Sleep and tiredness
- Sleep Foundation: Sleep Foundation
Written and reviewed by the Quiet Mind Sleep editorial team in line with our editorial policy. Spotted an error? Let us know.