Tog Ratings Explained: Which Duvet Weight Do You Actually Need?

"Tog" is a measure of thermal resistance — how well a material prevents heat from escaping. The higher the tog, the warmer the duvet. It's a British standard (BS 5335) developed in the 1940s, and it's reasonably reliable as a comparison between duvets of the same fill type.

One tog is equivalent to the thermal resistance of a light indoor jacket. A 2.5 tog duvet feels like a thin throw. A 13.5 tog is a serious winter duvet. The scale runs from around 1 (purely decorative) to 15 (the warmest available for domestic use).

Where tog becomes complicated is when you compare different fill types. A 10.5 tog goose down duvet will feel different from a 10.5 tog hollowfibre duvet — the thermal properties are approximately equivalent, but the down will feel lighter and more breathable for the same warmth rating.

For a typical UK home (which runs warmer in recent summers and has central heating in winter), a rough seasonal guide:

4.5 tog is appropriate for summer months or for warm sleepers year-round. It provides minimal warmth and is designed to be a light cover rather than insulation.

7.5–9 tog covers spring and autumn for most people — enough warmth for a bedroom at 17–18°C without being stifling.

10.5 tog is the most popular all-year-round weight in the UK, because most people keep their heating on in winter and the bedroom rarely drops below 15°C. This is the weight we'd recommend if you're buying one duvet and want it to work for most of the year.

13.5 tog is winter-specific — suitable for bedrooms that cool significantly overnight (below 14°C), for cold sleepers, or for those who prefer sleeping in a warm environment.

15 tog is for very cold bedrooms or very cold sleepers. If you sleep in a room that drops to 10°C overnight (an unheated room in an older property, for example), this is the appropriate choice.

The guides above assume an average body temperature. But "warm sleeper" and "cold sleeper" are genuinely different physiological states, not just preference.

Warm sleepers — those who regularly throw off covers, wake up damp, or feel overheated — should go one tog lower than the seasonal guide suggests. A warm sleeper in a 17°C bedroom in October might do better with a 7.5 tog than a 10.5 tog, and may need to supplement with extra blankets rather than a heavier duvet.

Cold sleepers — those who feel cold feet, layer in bed, or find themselves unable to warm up — should go one tog higher. A cold sleeper might find a 13.5 tog appropriate for most of the year, even in a centrally heated home.

Hormonal changes (including menopause and some medications) can dramatically shift how warm or cold someone runs. If your duvet requirements have changed significantly in recent years, this is worth factoring into a new purchase.

All-seasons duvets come as two separate duvets — typically a 4.5 tog and a 9 tog — that attach together with poppers or buttons to create a 13.5 tog winter duvet. You use them separately in summer and spring/autumn, and combined through winter.

The appeal is obvious: one purchase, three configurations. In practice, the quality varies significantly. A good all-seasons duvet (John Lewis do a well-regarded version, as does The White Company) genuinely works. A cheap one tends to have poor-quality attachment points that fail, and the fill quality to match the lower price.

One practical downside: pairing and separating the two duvets regularly is fiddlier than it sounds, and many people end up just using the combined version year-round. If you're buying one duvet and want to simplify, a 10.5 tog is a better answer for most UK homes.

Tog tells you about warmth. Fill type tells you about how that warmth is delivered — and this affects breathability, weight, and lifespan significantly.

Goose down is the premium option: light, breathable, excellent insulation, and (with quality fill power) compressible. A 10.5 tog goose down duvet from The White Company feels dramatically lighter than a synthetic equivalent at the same warmth rating. It's also more expensive, starting around £150–200 for a king.

Duck down is similar to goose down but typically from slightly younger birds with slightly lower fill power. It's meaningfully cheaper and still excellent — a good budget-to-mid option.

Synthetic hollowfibre is hypoallergenic, machine washable, and affordable. It clusters together over time and loses loft faster than down. Replace every 2–3 years for a mid-market synthetic; every 5+ for quality down.

Wool-filled duvets are a genuinely underrated option for temperature regulation. Wool breathes exceptionally well, wicks moisture, and adapts to body temperature — warm when cold, cool when warm. Naturalmat and Devon Duvets make excellent wool options.