The right mattress is the one that keeps your spine level in the position you sleep in, without pressing on your hips or shoulders hard enough to wake you. Everything else on this page is detail in service of that one sentence. Most people shop the other way round: they start with a brand, a price or the word orthopaedic, and get to their own body last.
Over seven years old, sagging where you lie, or leaving you stiffer at 7am than you were at midnight: any one of those puts you in the market, whether you planned to be or not.
How old is your mattress?
Seven years is the number to remember. That's the replacement point Bed Advice UK, the National Bed Federation's consumer arm, gives for a mattress in nightly use. Fillings compress and springs lose tension long before anything looks worn.
Ten years in, a bed can still feel fine to you and be doing nothing for your back, since you've adjusted to it a night at a time.1 Turn it over if it's double-sided, or rotate it head to toe if it isn't. If it's still dipping afterwards, the mattress has told you what you need to know.
What should you look for?
Comfort and support are two different jobs. Getting one doesn't mean getting the other. Support is the springs or the foam core holding your body straight from head to heel.2 Comfort is the top few centimetres deciding whether the surface presses on you or gives.
Put a firm base under a plush pillow top and you've got both. Under a thin cover, a soft base gives you neither, however good it feels in the shop for the first thirty seconds.
Whether you'll still like it in month three comes down to movement, temperature and edge. Movement: if your partner turning over wakes you, look for pocket springs or foam, which absorb motion instead of passing it across a linked coil.
Temperature: dense foam stores body heat, so hot sleepers do better on springs or on foam with an open cell structure.3 Edge: sit on the side of the bed and see whether it drops away. You'll spend more time there than you'd think, getting in and out and sitting to put socks on.
How firm should it be?
Firmer than you'd guess if you sleep on your back or front, softer than you'd guess if you sleep on your side. That's the whole rule and the rest is calibration.
Manufacturers' firmness ratings are their own steer about where a mattress sits within their range, formed by people who design beds for a living. Take that seriously inside the brand, but don't expect it to carry across to another one. One maker's medium is another's medium-firm.
Weight moves the dial too. Under about 10 stone (64 kg) you'll sink less, so a medium does the job a medium-firm does for someone heavier. Over 15 stone (95 kg) the pelvis drops further into the surface, so you step up a notch to keep the spine level. I'd rather see a heavier side sleeper on a medium-firm hybrid than on a soft all-foam bed, whatever the marketing says about contouring.
How do you sleep?
On your side
Your shoulder and hip carry most of your weight on two small patches, so they need to sink a little for the spine to stay straight. Side sleepers tend to do best between medium-soft and medium, roughly 4 to 6 on the ten-point scale many brands use. Too firm and the shoulder's pushed upwards, so the spine bends into an S. Dead arm, sore lower back, or both by morning.
On your back
Back sleepers need the lumbar curve held, not filled. Medium-firm, 6 to 7 out of ten, lets the buttocks settle while the small of the back stays supported. Softer than that and the pelvis sinks past the hips, which is the position most likely to leave you stiff by morning when you're fine standing up.
On your front
Firm, and think about changing. Front sleeping arches the lower back and turns the head to one side for hours at a stretch. Even the firmest mattress only limits the strain. Retrain yourself onto your side with a pillow between your knees. I'd back that change over any mattress on this site.
What size do you need?
Buy the biggest bed the room will take. Two people on a standard double (135 cm wide) each get less width than a child in a single. It's why so many people who sleep badly at home sleep fine in a hotel king. Measure the room with the door swing and the bedside tables in place before you fall for a super king.
| Size | Imperial | Metric |
| Small single | 2'6" x 6'3" | 75 x 190 cm |
| Single | 3' x 6'3" | 90 x 190 cm |
| Small double | 4' x 6'3" | 120 x 190 cm |
| Double | 4'6" x 6'3" | 135 x 190 cm |
| King | 5' x 6'6" | 150 x 200 cm |
| Super king | 6' x 6'6" | 180 x 200 cm |
Which material?
None of them is best. Each construction trades one property for another, and the right one for you depends on how you sleep, how warm you run and how much you weigh. Plenty of what's sold in the UK combines two or more of them, which is where the word hybrid comes from.
Memory foam
Memory foam softens with body heat and moulds to you, so it spreads your weight across the whole contact area and takes pressure off the hip and shoulder. Side sleepers and people with joint pain like it for that reason. That same property's the catch. It stores heat and it's slow to respond, so hot sleepers and people who change position a lot often find it clammy or hard to move in.
Look for open-cell or gel-infused foam if you run warm. Expect a firmer feel on a cold night too, because the foam doesn't soften until it's warmed through.
SHOP MEMORY FOAM MATTRESSES
Pocket springs
Each spring sits in its own fabric pocket and moves on its own, so the mattress follows the shape of two different bodies without one disturbing the other. Air moves freely through a spring unit, which makes this the cooler option. Well-made pocket springs with natural fillings also tend to keep their shape longer than foam.
Spring count's a weaker guide than the sales floor suggests. 1,000 well-tensioned springs in a king can outperform 3,000 thin ones, because wire gauge and tension decide the support, not the number. The difference between two sprung beds is in the comfort layer. Check what's between you and the springs.
SHOP POCKET SPRING MATTRESSES
Latex
Latex is springy rather than slow, so it cushions like foam but pushes back straight away when you turn. Because it's dense it's less hospitable to dust mites than loose fillings, though you'll still want a washable protector over it. Natural latex comes from rubber tree sap. Synthetic and blended versions are cheaper and less resilient, and the label doesn't always say which you're getting.
Its drawbacks are weight and heat. A king latex mattress is a two-person lift to rotate, and it runs warmer than springs, though not as warm as memory foam.
SHOP LATEX MATTRESSES
Open coil
Open coil, sometimes sold as traditional sprung, links every spring to its neighbours with wire. It's the cheapest construction and the one I'd steer most adults away from. When one spring compresses the ones beside it follow, so a partner's movement travels across the bed.
Give it a couple of years and a roll-together dip tends to form in the middle. It's got a place in a spare room or a child's first bed. As the main bed for two adults it doesn't.
Do you sleep hot?
Wake up damp and the mattress is part of it. Foam of any kind stores heat because there's nowhere for it to go. Springs let air through and let the heat out.
Night sweats are the strongest single reason to choose a sprung or hybrid bed over an all-foam one. Cooling gel doesn't change that order; it only narrows the gap.
What should you pay?
Work it out per night, not per mattress. Spend £600 on a bed that lasts seven years and it's cost you about 23p a night. At £1,200 it's about 47p, which puts the gap between them at less than a cup of tea a week.
Price tracks the spring count, the depth and quality of the fillings and the brand's overheads more than the headline material. A good pocket spring bed and a good foam bed from the same tier often cost about the same.
Two habits save more than any voucher. Check the price history on a product page before you believe a "was" price. And use the trial where one's offered. Bed-in-a-box brands commonly run a 100-night trial, which gets you past the two to three weeks a new mattress takes to settle with time to spare.
Who should see a GP before buying?
A mattress isn't a treatment. If your back pain is constant regardless of the time of day, or comes with numbness, tingling or weakness in a leg, see your GP before you spend anything. NHS guidance on back pain lists the signs that need a doctor rather than a shop.
Stiffness that's there when you wake and gone once you're moving puts the bed on the suspect list. Our back pain guide goes through firmness by position in more detail than there's room for here.
Buy for the body you have, in the position you sleep in, at the size the room allows, and give it three weeks before you judge it. The rest is upholstery.
