How to Choose a Mattress: Firmness, Springs and Foam

Most UK sleepers should buy a medium-firm pocket sprung or hybrid mattress with 1,000 to 2,000 springs, sized to the bed already in the room; a UK double is 135 by 190cm. Side sleepers suit medium, back and front sleepers suit firmer. Rotate it every three months and expect to replace it at around eight years.

A mattress gets roughly eight hours of use a night for eight years and is bought about as often as a boiler, which is why almost nobody feels confident doing it. This guide settles firmness first, then construction, spring count, depth and the size checks; in the order you need them, for a main-bedroom purchase in the £300–£900 band.

What this guide covers

• What mattress firmness should you buy?
• Which construction suits what you care about most?
• Is pocket sprung or memory foam better?
• How many springs should a mattress have?
• What is a hybrid mattress, and is it worth paying for?
• Mattress depth decides which bedding fits
• Buy the mattress to fit the bed already in the room
• A rolled mattress needs a day or two before it feels right
• A topper changes the feel, not the support
• Rotate every three months, replace at around eight years
• What Marqet stocks, and what we would buy
• Frequently asked questions

What mattress firmness should you buy?

Medium-firm suits more UK sleepers than any other single answer, but the correct firmness is set by two things working together: the position you fall asleep in, and your body weight. Position decides where the mattress has to yield — the shoulder and hip for a side sleeper, the lumbar curve for a back sleeper. Weight decides how far it will yield before it stops.

That is why one mattress described as "medium" feels plush to someone of 18 stone and hard to someone of nine. Read the table down your sleeping position, then across to your weight band.

One honest caveat the trade rarely prints: there is no British Standard for mattress firmness. "Medium" is a manufacturer's word, not a measured value, so one brand's medium-firm genuinely can be another's medium. Use the words to shortlist, then judge the mattress on its construction and depth, which are stated as numbers and therefore comparable.

Which construction suits what you care about most?

Choose the construction from the one thing that would most annoy you about a bad mattress, not from the marketing name. Five complaints cover almost every return: it does not hold me up, I feel every time my partner moves, I get too hot, it cost too much, and it collects dust. Each has a different right answer.

Latex sits outside that list: bouncier and cooler than memory foam, more durable than either, appreciably heavier, and the most expensive mainstream construction. Shortlist it if you dislike the sinking feeling of foam but want more contour than springs alone give.

Is pocket sprung or memory foam better?

Pocket sprung is the better all-round buy for most UK bedrooms, because it breathes, holds its edges and works for every sleeping position. Memory foam wins decisively on exactly two things: isolating movement, and contouring closely to a side sleeper's shoulder and hip.

A pocket sprung mattress holds each spring in its own fabric pocket, so a 90kg hip and a 12kg calf are supported by different springs at different depths. Air passes between the pockets, which is why sprung mattresses shed body heat better than solid foam. The edges stay firm enough to sit on while you put your socks on; a small thing that becomes a daily thing.

Memory foam is viscoelastic: it softens where your body warms it and firms again as it cools. That gives the close, moulded feel people either love or cannot settle on, and it means almost no movement travels across the bed. The trade-off is heat. If you are the person who kicks a leg out from under the duvet at 3am, put foam at the bottom of the shortlist and read our guides to choosing a duvet tog and keeping a bedroom cool alongside this one.

Marqet's position: unless motion isolation is the problem you are solving, buy springs with foam on top rather than foam alone. You get the contour without giving up the airflow.

How many springs should a mattress have?

Between 1,000 and 2,000 pocket springs in a 135 by 190cm double is the range worth paying for. Below roughly 800 the support becomes coarse, because each spring is covering too much area. Above roughly 2,000 in a double the springs have to be made from thinner wire to physically fit in the same 2.57 square metres, so a higher number stops meaning more support and starts meaning finer springs.

Three things make spring counts harder to compare than they look:

• The count usually refers to a king size. UK spring counts are conventionally quoted for a 150 by 200cm king. A double of the same model contains fewer actual springs at the same density, so check the size the number applies to before comparing two mattresses.
• Micro-spring layers inflate the headline. A mattress advertised at 3,000 springs is often a 1,000-spring support unit with a 2,000 micro-spring comfort layer above it. That layer does useful work on feel, but it is not 3,000 springs holding your spine up.
• Wire gauge matters as much as count. Spring wire in a mattress typically runs between about 12 and 15 gauge, and a lower gauge number means thicker wire and a firmer spring. A 1,200-spring unit in thicker wire can support a heavier sleeper better than a 2,400-spring unit in thin wire.

Open coil mattresses are counted differently; usually 250 to 400 coils in a double, joined into one unit; and that number is not comparable with a pocket count.

What is a hybrid mattress, and is it worth paying for?

A hybrid is a pocket sprung support unit with a substantial foam, gel or latex comfort layer bonded on top, usually finishing at 25 to 32cm total depth. It is worth paying for when you want the contour of foam and the airflow of springs, which describes most couples who cannot agree on feel.

What to look at on a hybrid listing: the depth of the comfort layer, not just the total. A 28cm hybrid with a 2cm foam layer behaves like a pocket sprung mattress; the same depth with a 6cm layer behaves much more like foam. If the listing gives the layer breakdown, it is telling you something the firmness word cannot.

Mattress depth decides which bedding fits

Mattress depth in the UK runs from about 15cm to over 35cm, and the number matters twice: it decides which fitted sheet will stay on, and it decides how high you end up sitting on the bed. Measure the mattress you are replacing before you order bedding for the new one.

Depth compounds with the base. A 30cm mattress on a standard divan puts the sleeping surface around 70cm off the floor, which is high enough to matter if you are short, elderly or buying for a child's room. It also eats headboard height, so a low headboard can end up barely clearing the pillows. Our guides to choosing a divan, ottoman or bed frame and to buying bed linen pick up both of those threads.

Buy the mattress to fit the bed already in the room

UK mattress sizes are fixed: single 90 by 190cm, small double 120 by 190cm, double 135 by 190cm, king 150 by 200cm and super king 180 by 200cm. Mattresses match those figures exactly, so unless you are replacing the base at the same time, the size decision is already made for you by the frame.

Two traps. First, UK sizes are not US or European sizes — a UK king at 150 by 200cm is closer to a US queen than to a US king, and a European king is 160 by 200cm, ten centimetres wider than ours. A mattress bought to a US or EU chart will not fit a UK frame or a UK fitted sheet. Second, if you are also upsizing the bed, check the room before the mattress: going from a double to a king adds 15cm of width and 10cm of length, and that is often the 15cm that was your walking space. The full set of dimensions, in centimetres and inches, with the clearance each one needs, is in our UK bed sizes and mattress dimensions chart.

A rolled mattress needs a day or two before it feels right

Most rolled mattresses are usable within four to six hours of being unwrapped and reach their stated height in 24 to 72 hours. Unroll it onto the base it will live on, cut the plastic rather than dragging the mattress out of it, and leave the room ventilated for the first day.

Temperature is the variable people miss. Compressed foam recovers faster at around 18 to 21C, so a mattress unrolled in a cold spare room in February can look under-inflated a full day longer than the label suggests. The new-product smell dissipates over the same period with a window open, and foam settles measurably over the first few nights; which is why buying one grade firmer than you think you want is the safer error.

A topper changes the feel, not the support

A 5 to 8cm topper can soften a mattress that turned out firmer than you wanted, and it cannot fix one that has lost its support. If there is a visible dip or you can feel a spring through the fillings, a topper hides the symptom for a few months and nothing more.

Where toppers earn their place: matching two sleepers of different weights on one mattress, and adding contour to a firm pocket sprung mattress without moving to foam. Remember the depth arithmetic; a 28cm mattress plus a 7cm topper is a 35cm bed, and needs an extra deep fitted sheet. A protector is a different product doing a different job: a thin washable barrier that keeps perspiration, spills and dust out of fillings you can never launder, and the cheapest thing you can do to make a mattress last its full term.

Rotate every three months, replace at around eight years

Rotate any mattress head to foot roughly every three months, and only turn it over if it has sleeping fillings on both faces. Most modern pocket sprung, foam and hybrid mattresses are single-sided and labelled no-turn, because the comfort layer is built on one face only; flipping one of those puts you on the support base.

Plan on replacing a mattress in nightly use at around seven to eight years. That is a wear guideline rather than an expiry date, and the signals matter more than the number: a dip you can see when the bedding is off, springs you can feel through the fillings, or waking up stiffer than you went to bed. A guest-room mattress used a few weeks a year will comfortably outlast it.

One smaller point decides whether a mattress reaches eight years at all: slat gaps should be no wider than about 7cm, because wider gaps let the mattress sag between them and most manufacturers make that a guarantee condition.

Rotate every three months, replace at around eight years

Rotate any mattress head to foot roughly every three months, and only turn it over if it has sleeping fillings on both faces. Most modern pocket sprung, foam and hybrid mattresses are single-sided and labelled no-turn, because the comfort layer is built on one face only; flipping one of those puts you on the support base.

Plan on replacing a mattress in nightly use at around seven to eight years. That is a wear guideline rather than an expiry date, and the signals matter more than the number: a dip you can see when the bedding is off, springs you can feel through the fillings, or waking up stiffer than you went to bed. A guest-room mattress used a few weeks a year will comfortably outlast it.

One smaller point decides whether a mattress reaches eight years at all: slat gaps should be no wider than about 7cm, because wider gaps let the mattress sag between them and most manufacturers make that a guarantee condition.

What Marqet stocks, and what we would buy

Marqet lists 135 products across mattresses and bedroom, of which 131 were in stock at the last full check in September 2026 — 97%, the healthiest availability of any family on the site. The dedicated mattresses shelf holds 35, divan and ottoman beds 22, and bedding 179, so the mattress, the base and the linen can be sized against each other in one order.

The two names a UK reader will recognise are the deepest here: 62 products on the Silentnight shelf and 22 on the Sealy shelf, both long-established British bed manufacturers. Across beds and mattresses the measured median price was £516.99 in September 2026, and the range most main-bedroom buyers shop sits at typically £300–£900 at the time of writing.

What we would actually buy for a main bedroom double: medium-firm, pocket sprung or hybrid, 1,000 to 2,000 springs quoted at the size we are buying, 25 to 30cm deep, with a washable protector on top from day one. We would spend the money on wire gauge and comfort-layer depth before spending it on a 3,000-spring headline, and we would not buy an all-foam mattress for a south-facing bedroom.

What mattress firmness is best for side sleepers?

Side sleepers usually want medium or medium-soft, because the shoulder and hip have to sink in far enough to keep the spine level. A lighter side sleeper under about 11 stone is better off on medium-soft; a side sleeper over about 16 stone should move up to medium-firm, because a softer mattress will bottom out under the hip.

Is pocket sprung or memory foam better?

Pocket sprung is the better all-round buy for most UK bedrooms because it breathes, holds its edges and suits every sleeping position. Memory foam wins on two specific things: isolating movement so one person turning over does not wake the other, and closely contouring a side sleeper's shoulder and hip. Foam also runs warmer.

How many springs should a mattress have?

Between 1,000 and 2,000 pocket springs in a 135 by 190cm double is the useful range. Below roughly 800 the support is coarse; above roughly 2,000 the springs have to be made from thinner wire to fit in the same area, so the headline number stops telling you anything about support. Check which bed size the count refers to.

How long does a rolled mattress take to expand?

Most rolled mattresses are usable within four to six hours of being unwrapped and reach full height in 24 to 72 hours. A cold room slows it down, because compressed foam recovers faster at around 18 to 21C. Give it a few nights before judging the firmness, as foam softens slightly once it has been slept on.

How often should you replace a mattress in the UK?

Around every seven to eight years for a mattress in nightly use, and sooner if there is a visible dip, a spring you can feel through the fillings, or you wake stiffer than you went to bed. Guest-room mattresses used a few weeks a year will last considerably longer. Rotation extends the life; it does not reset it.

Should you turn or rotate a mattress?

Rotate every mattress head to foot roughly every three months. Only turn it over if it is a two-sided mattress with sleeping fillings on both faces. Most modern pocket sprung, foam and hybrid mattresses are single-sided and labelled no-turn, and flipping one puts you on the base layer rather than the comfort layer.

Shop the sleep range at Marqet

Start with mattresses and bedroom for the full 135-product family, or go straight to the mattresses shelf if the base is staying. If the base is being replaced too, divan and ottoman beds is where the storage options live, and bedding carries the deep fitted sheets and protectors the depth table above points to.