The highest tog duvet you can buy in the UK is 18 tog, and it's sold as an all-season set: a 4.5 tog and a 13.5 tog duvet joined together. As a single duvet, the scale runs to 16.5 tog, and many shops stop at 15 tog. Below: what tog measures, what the warmest duvet is, whether 15 tog is too hot, who a 15 tog suits, how combinations reach 15 and 18 tog, why weight doesn't equal warmth, and why babies and young children need much less.
| Tog | How it's sold | Typical use |
|---|---|---|
| 1 to 2.5 | Single duvet | Minimal warmth, hot nights |
| 3 to 4.5 | Single duvet | Summer |
| 7.5 to 10.5 | Single duvet | Spring and autumn |
| 12 to 13.5 | Single duvet | Winter |
| 15 | Single duvet, or 4.5 + 10.5 tog joined | Cold bedrooms in winter |
| 16.5 | Single duvet | Extra warm |
| 18 | 4.5 + 13.5 tog joined | The coldest nights |
The bands from 1 to 13.5 tog and the 16.5 tog top step come from the UK tog scale on Wikipedia. The 15 and 18 tog combinations are those Soak&Sleep sells.
What does tog mean on a duvet?
Tog is a unit of thermal resistance: it measures how well a duvet holds in your body heat. One tog equals 0.1 m²K/W, so a 15 tog duvet resists heat loss ten times as well as a 1.5 tog duvet.
The tog was devised in 1946 by F. T. Peirce and W. H. Rees at the Shirley Institute in Manchester. The test that measures it, the Shirley Togmeter, is set out in British Standard BS 4745:2005. Wikipedia notes that stated duvet togs are minimums, and the real figure may be up to 3 tog higher. The figures also assume no duvet cover, which traps a little extra air. Our guide to what tog means covers the test in more detail.
What is the warmest duvet?
The warmest duvet on general sale in the UK is an 18 tog all-season set. As one piece, a 16.5 tog duvet is the warmest step on the British scale, and 15 tog is the top of many shops' ranges.
Wikipedia describes British duvets as coming in 1.5 tog steps from 3 to 16.5 tog, and calls 16.5 tog extra warm. Belledorm's tog guide gives a scale from 2.5 up to 15. So the answer depends on the shop: some stop at 13.5 tog, some at 15, and a few go to 16.5 as a single duvet.
Is there an 18 tog duvet?
Yes, 18 tog duvets exist, and they're made by joining two lighter duvets. Soak&Sleep pairs a 4.5 tog with a 13.5 tog duvet and sells the set in single, double, king and super king.
Soak&Sleep says the 18 tog set is meant for the coldest nights, for people who feel the cold, sleep in cooler bedrooms or like a very cosy bed. The two halves come apart, so the same set gives you a 4.5 tog for summer and a 13.5 tog for spring and autumn. We haven't found a single-piece 18 tog duvet on the British tog scale.
Is 15 tog too hot?
A 15 tog duvet can be too hot in a heated bedroom, because it's warmer than the UK winter band of 12 to 13.5 tog. It's made for cold rooms and winter nights, and for people who feel the cold.
The Sleep Charity says bedrooms should ideally be around 16 to 18°C. If your room stays in that range and you sleep warm, a 10.5 or 13.5 tog will usually be enough. The Sleep Charity's advice for hot nights is to swap the duvet for a cotton sheet or a low tog duvet. Waking up hot under a 15 tog is the sign to drop down a step. Our winter tog guide compares 13.5 and 15 tog for colder months.
Who is a 15 tog duvet for?
A 15 tog duvet is for people who sleep in a cold bedroom, keep the heating off overnight, or feel the cold more than their partner. It's a winter duvet, not a year-round one.
The test is simple. If your bedroom falls below The Sleep Charity's 16 to 18°C on winter nights and you still feel cold under a 13.5 tog, a 15 tog is the next step up. Our own product page puts 13.5 to 15 tog in the bracket for cold bedrooms and winter.
In spring and summer a 15 tog is far more warmth than you need, so plan on a lighter duvet for the rest of the year. Our duvet tog guide sets out every step from 1 to 15.
How do all-season duvets reach 15 tog or more?
All-season duvets reach 15 tog or more by fastening two duvets together with poppers or ties. The togs add up: 4.5 + 10.5 makes 15 tog, and 4.5 + 13.5 makes 18 tog.
Soak&Sleep lists 4 combinations on selected ranges: 7.5 tog (3 + 4.5), 13.5 tog (4.5 + 9), 15 tog (4.5 + 10.5) and 18 tog (4.5 + 13.5). Dunelm also sells a 15 tog duo made from a 4.5 and a 10.5 tog. The classic all-season set on Wikipedia is 4.5 + 9 tog, which joins to 13.5 tog. Joined sets suit you if you want one purchase for every season. A single 15 tog duvet suits you if you only need extra warmth in winter.
Is a heavier duvet warmer?
No, a heavier duvet isn't automatically warmer, because tog measures thermal resistance, not weight. Belledorm says heavier duvets don't necessarily mean more warmth: the filling material decides how much heat a duvet holds.
Two duvets with the same tog give the same warmth, even if one weighs more. So compare duvets by the tog on the label, not by how heavy the box feels. Our microfibre duvet weighs around 1.2 to 2.2 kg, depending on size. Our guide to what hollowfibre is explains how the hollow fibres hold warm air.
Can babies and children use a high tog duvet?
No, babies under 12 months shouldn't have any duvet, whatever the tog. The NHS says not to use pillows, duvets, cot bumpers, loose blankets or soft toys in a baby's cot.
The NHS warns that overheating can increase the risk of sudden infant death syndrome, and that too much bedding is one cause. The NHS and The Lullaby Trust both advise a baby's room at 16 to 20°C. The Lullaby Trust doesn't publish a tog chart, because the insulation of each product varies. For toddlers over 12 months, children's duvets are sold in lighter togs: ours come in 4.5, 7.5 and 9 tog. Our toddler tog guide covers which one to pick.
What is the highest tog duvet at Adam Home?
The highest tog we sell is our 15 tog duvet, the warmest of 7 tog options from 1 to 15. It has a hollowfibre down-alternative filling, with no feathers, held in stitched channels.
Our 15 tog duvet comes in single, double, king and super king, from £20.99 for a single. The same listing covers 1, 2.5, 4.5, 7.5, 10.5 and 13.5 tog, from £15.99. It's machine washable, and the product page suggests allowing 24 hours for it to loft fully after unpacking. We don't sell an 18 tog duvet or a joinable all-season set.
Written by the Adam Home team in the UK.
