Bedding Explained: Thread Count, GSM, Tog and What They're Worth

Bedding is a category where a single number took over the marketing and never left. Thread count is printed larger than anything else, compared across brands as though it were standardised, and used to justify substantial price differences — while the properties that actually determine how a sheet feels after fifty washes go unmentioned.

This guide sets out what each figure measures and which ones survive scrutiny.

Thread count: what it measures and how it's inflated

Thread count is the number of threads in a square inch of woven fabric, counting warp and weft together. As a measure of density it is real, and up to a point it correlates with a fabric feeling substantial rather than thin.

The inflation happens through ply counting. Yarns can be spun from several finer strands twisted together, and counting each of those plies individually multiplies the headline figure without adding density. A fabric woven from two-ply or four-ply yarns can be presented at two or four times the count of the equivalent single-ply construction — which is how figures reach levels that would be physically implausible in a single-ply weave.

There is a practical ceiling, too: past a moderate count in a standard weave, packing more threads in requires finer or multiple yarns, and the fabric becomes denser, heavier and less breathable rather than better. Above that point the number is a marketing variable rather than a quality one — the classic pattern described in product specifications explained.

Fibre and staple length matter more

What the thread is made of matters more than how many of them there are.

Staple length — the length of the individual fibres — is the single best predictor of how cotton bedding will age. Longer fibres produce smoother, stronger yarns with fewer protruding ends, which means less pilling, less roughening and better durability. Extra-long staple cottons are sold under regional and varietal names, and a brand naming the fibre type is disclosing something checkable.

Fibre type sets the behaviour: cotton is breathable and launderable; linen is stronger, highly breathable and softens with use while creasing freely; regenerated cellulosics such as viscose, modal and lyocell drape smoothly and feel cool but are typically weaker when wet; polyester blends resist creasing and cost less while breathing less well. The vocabulary is covered in fabric composition explained.

A useful heuristic: where a listing states thread count prominently but not fibre type, staple length or weave, the count is doing promotional work.

Weave: percale, sateen, jersey and linen

Weave determines feel more directly than any number, and the same cotton in two weaves produces two entirely different sheets.

Percale is a plain weave, one thread over and one under. Crisp, matte, breathable, and the classic hotel feel. It tends to soften with washing rather than degrade.

Sateen floats several threads over one before going under, exposing more thread surface. Smoother, more lustrous, warmer to the touch, and more prone to snagging because of those exposed floats.

Jersey is knitted rather than woven — soft, stretchy, T-shirt-like, warm, and prone to pilling depending on the yarn.

Linen uses flax fibres in a plain weave, with a characteristic slubby texture, excellent breathability and a creased appearance that is intrinsic rather than a fault.

Choose the weave first, then the fibre, then let thread count be a tie-breaker. That order matches how the fabric will actually feel in the bed.

GSM for towels and blankets

Grams per square metre is a weight measure, and it is more honest than thread count because it is much harder to game — you cannot inflate mass by counting it differently.

For towels, higher GSM means denser pile: more absorbent, more substantial, slower to dry, and heavier in the wash. Lower GSM dries faster and suits gym and travel use. Neither is better; they suit different jobs.

For blankets and throws, GSM indicates substance and warmth for a given fibre, and is the most comparable figure available.

For sheets, GSM is published less often but is more informative than thread count when it is, because it describes the fabric rather than the counting convention.

Tog ratings and how to choose one

Tog measures thermal insulation. It is not a measure of quality, filling type or weight, and two duvets at the same tog can feel entirely different depending on what is inside them.

The right rating depends on three things that vary by household: your bedroom temperature, how warm you sleep, and what else is on the bed. A cold bedroom and a cool sleeper need more insulation than a warm room and a warm sleeper, and seasonal advice that ignores the room is unreliable.

Two practical approaches. All-seasons sets combine a lighter and a heavier duvet with fastenings so they can be used separately or together, which covers the range without buying three duvets. And where two people disagree about warmth, separate duvets solve a problem no tog rating can.

A note on children's bedding: follow the manufacturer's and recognised safety guidance on when a duvet is appropriate and at what rating, rather than a general rule from an article.

Fillings: down, feather and synthetic

Down is the fine under-plumage. It traps air efficiently, giving warmth for very little weight. Fill power measures its loft — the space a given weight of down occupies — so it describes warmth for weight rather than total warmth. Total warmth also depends on the quantity of fill, quoted separately in grams, which is why the two figures must be read together.

Feather is heavier, less lofty and cheaper, and blends are common; the proportion of down to feather is the figure to read.

Synthetic fillings — usually polyester in hollowfibre or microfibre form — are washable at home, generally easier to care for, and cheaper. Microfibre mimics down's softness more closely; hollowfibre is bouncier. Synthetics typically flatten sooner than good down.

Two things to check regardless of filling: whether the construction is baffled or simply stitched through, since stitch-through creates cold spots at the seams, and whether the item is home-washable, because professional cleaning is a recurring cost that belongs in the arithmetic in cost per use.

Sizing traps in UK bedding

Bed sizes and bedding sizes are not the same conversation, and three traps recur.

Duvet size is not mattress size. A duvet needs enough overhang for the bed's height and for two people, so the same nominal size can be too small on a deep mattress.

Mattress depth defeats fitted sheets. Deep, pillow-top and topper-equipped mattresses need a stated sheet depth, and this is the most common bedding return.

International sizes do not map cleanly. UK, EU and US size names overlap while the dimensions differ, so a size name imported from another market may not fit a UK bed at all.

The fix is the same in every case: buy on centimetres, not names. Measure the mattress including depth, and compare against the stated dimensions rather than the label — the same measure-first discipline as in how to judge product quality online.

Care and how long bedding should last

Bedding is laundered more than almost anything else you own, so care behaviour is durability behaviour.

Read the care label before buying, not after: temperature limits, whether tumble drying is permitted, and whether a duvet or pillow is home-washable are all running costs in disguise, as set out in care labels explained. Washing cooler and drying gently extends life for most fibres, and elastane in fitted sheets degrades with heat, which is why fitted sheets usually fail before flat ones.

Rotating between two or three sets spreads wear and gives fabrics time to recover, which measurably extends the life of all of them. And because bedding is used every single night, the denominator in any cost calculation is enormous — which is exactly the case where paying for better fibre and construction repays, provided you buy the weave you actually like sleeping under.

Frequently asked questions

Is a higher thread count better?

Only up to a point, and only when counted honestly. Very high figures are commonly reached by counting the plies within twisted yarns. Beyond a moderate count in a standard weave, fibre quality, staple length and weave predict feel and durability far better.

What is the difference between percale and sateen?

They are weaves, not fibres. Percale is a plain weave — crisp, matte, breathable. Sateen floats threads over one another for a smoother, more lustrous, warmer surface that snags more easily.

What tog rating should I choose?

Tog measures insulation, not quality. The right figure depends on your bedroom temperature and how warm you sleep, not the season alone. All-seasons sets covering the range are a practical answer.

Does fill power tell me how warm a duvet is?

Not alone. Fill power describes the loft of down — warmth for weight — while total warmth also depends on the quantity of fill, quoted separately. Read the two together.

How we write this guide

This article is research-led. It draws on established textile conventions — thread count as threads per square inch and the ply-counting practice that inflates it, staple length as a predictor of yarn smoothness and durability, the structural differences between plain, sateen and knitted constructions, grams per square metre as a weight measure, tog as a measure of thermal insulation, and fill power as a measure of down loft distinct from fill quantity.

We publish no thread counts, GSM figures, tog values, fill powers or bedding dimensions: conventions vary by manufacturer and market, sizes differ between the UK, EU and US, and the right tog depends on a bedroom we cannot see. Buy on stated centimetres and on the manufacturer's own figures. No products were tested, named or ranked, and guidance on bedding for infants and young children should come from the manufacturer and recognised safety advice rather than from this guide.

Recommended Today may earn commission from links to retailers. Commission does not influence our editorial content or the order of any recommendation. This guide is reviewed at least every 18 months. Next scheduled review: February 2028.