Grams per square metre, the only bedding number that means anything

Bedding is sold on a single number that stopped being meaningful twenty years ago. Thread count counts threads per square inch, and once mills began using multi ply yarns and counting each ply separately, a 300 thread count sheet could be advertised as 1,200. The number is now close to useless above about 400 and actively misleading above 600.

What to count instead

For cotton, staple length. Long staple cotton, meaning fibres of about 3.4 centimetres and above, spins into a smoother, stronger yarn with fewer ends at the surface, which is why it feels better and pills less. Extra long staple, above 3.8 centimetres, is the top of the market. The origin names on the label are a proxy for this and an imperfect one, since the terms are not consistently protected.

For linen, weight in grams per square metre. Under 150 is a summer sheet that will thin in a few years. 170 to 200 is the range that lasts a decade and a half and softens throughout. Above 220 is upholstery weight and will feel stiff on a bed for a long time before it gives in.

Weave, which decides how it feels

• Percale: a simple one over one over weave. Crisp, matte, cool, the hotel feel. Gets softer without getting slippery.
• Sateen: more surface threads floating over fewer. Smooth, slightly lustrous, warmer to sleep in, and it snags more easily because those floating threads are exposed.
• Linen plain weave: textured, irregular, highly breathable, wrinkled by nature and by design.
• Jersey, which is knitted rather than woven: comfortable, cheap, and it loses its shape within a couple of years.

Percale for anyone who sleeps warm, sateen for anyone who sleeps cold, linen for anyone in a climate with real summers and for anyone who has stopped caring about a smooth bed, which is most people who have tried it.

A 1,200 thread count sheet is either a very dense weave that sleeps hot, or a 300 thread count sheet with the arithmetic done creatively.

The finishing question

A great deal of inexpensive bedding is treated to feel soft in the shop. Silicone softeners and resin finishes give an immediate hand feel that washes out in five or six cycles, after which the sheet feels noticeably worse than it did on day one. Good bedding usually feels slightly less impressive in the packet and better after a month.

Look for a statement that the fabric is finished without formaldehyde resins, or for an independent textile certification. Both correlate with a mill that has nothing to hide in the finishing department.

The arithmetic

A linen set at 400 lasting eighteen years costs about 22 a year. A cotton set at 150 lasting six years costs 25 a year, and it will feel worse in years four and five. The expensive option is cheaper by the year and considerably better for the last decade of it, which is the same shape as almost every other calculation on this site.

The caveat is honest: linen takes about two years and roughly thirty washes to reach its good state, and a lot of people give up in month three. If crisp smoothness is what you want in a bed, buy percale and do not spend the extra.

Washing, which is where sets are lost

Forty degrees, no fabric softener ever, because softener coats the fibre and destroys the absorbency that makes natural fibres pleasant. Line dry or tumble on low and remove slightly damp. Wash at sixty only when there is a reason, because heat shortens the life of every fibre and the hygiene argument is weaker than the marketing suggests for a bed slept in by healthy adults.

Rotate between two sets rather than washing one repeatedly. Fibre recovers between uses, and two sets alternating will outlast three sets used in sequence.

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