Duvet Tog Ratings: 5 Questions, Answered
A tog is a measure of thermal resistance, and it tells you how well a duvet traps body heat. The higher the number, the warmer the duvet. A 4.5 tog duvet is for summer, a 10.5 tog sits in the middle for year-round use, and a 13.5 tog is the standard winter weight in the UK. Tog ratings are tested under BS 4745, the British Standard for textile thermal resistance, so a 13.5 tog from one brand should deliver roughly the same warmth as a 13.5 tog from another.
๐ Key Takeaways
- A tog measures warmth, not quality - a cheap 10.5 tog duvet can be just as warm as an expensive one; the number is about thermal resistance, not fill type
- Match the tog to the season - 4.5 tog for summer, 9-10.5 tog for spring and autumn, 13.5 tog for winter; an all-seasons combi set covers all three
- Room temperature matters more than the number - a 13.5 tog in a 22C room will overheat you; a 4.5 tog in a 12C room will leave you cold
- The BS 4745 standard keeps ratings honest - tog values are lab-tested on flat surfaces, so real-world warmth depends on your mattress, pyjamas and room temperature too
๐ Suggested Reading: 9 Tog Duvet: What It Means and When to Use It ยท 12 Tog vs 13.5 Tog Duvet: Which Warmth?
What Does 4.5 Tog Mean?
A 4.5 tog duvet is the lightest standard weight you will find in UK shops, and it is built for summer. It traps just enough warmth to take the chill off an open-window night without pushing your body temperature up. If you sleep hot or your bedroom stays above 18C through the warmer months, this is the rating to reach for.
The fill matters alongside the tog. A Utopia Bedding 4.5 Tog King uses a hollowfibre polyester fill that weighs about 200gsm, which keeps the duvet light and breathable. Down-filled 4.5 tog duvets cost more but feel airier because natural clusters trap less stagnant air than synthetic batting. Either way, the tog number is the same. For more detail on warm-weather picks, our best summer duvets guide covers the full range.
What Does 9 Tog Mean for Temperature?
A 9 tog duvet sits in the spring and autumn zone. Most UK bedrooms hover between 15C and 18C during those seasons, and a 9 tog layer holds enough warmth to keep you comfortable without the bulk of a winter quilt. It is the rating most people reach for when the 4.5 tog feels too thin but the 13.5 tog feels like overkill.
In practice, a 9 tog duvet works well from March through May and again from September to November. If you keep your bedroom windows closed and run heating intermittently, this is the sweet spot. Our 9 tog duvet guide goes deeper on fill types and seasonal timing.
What Does 12 Tog Mean?
A 12 tog duvet is a warm-weather winter option. It sits between the 10.5 tog year-round weight and the 13.5 tog full winter layer, and it suits people who run a bit warm or who keep their bedroom heated above 16C during the colder months. If you have ever woken up sweating under a 13.5 tog duvet, dropping to 12 tog might be the fix.
12 tog duvets are less common in high-street shops than 10.5 or 13.5, but they show up regularly on Amazon and at John Lewis. The Slumberdown All Seasons King ships with a 9 tog layer that sits close to this warmth level. The difference between 12 and 13.5 tog is noticeable once you have tried both. For a direct head-to-head, see our 12 tog vs 13.5 tog comparison.
What Does 13.5 Tog Mean?
A 13.5 tog duvet is the UK's standard winter weight. It is the rating you will find on most "winter" labelled duvets in Argos, John Lewis and Amazon, and it delivers the warmth most people need when bedroom temperatures drop below 15C. The Silentnight So Snug 13.5 Tog is a popular hollowfibre option that keeps the price under thirty pounds for a king size.
A 13.5 tog duvet also forms one half of the all-seasons system. The Slumberdown All Seasons King ships as two separate duvets, a 4.5 tog and a 9 tog, that clip together with press studs to create a combined 13.5 tog layer. That way you get summer, spring, and winter warmth from a single purchase.
One thing to watch: if your bedroom is well heated above 16C through winter, a 13.5 tog duvet can push your body temperature too high. Overheating at night increases the number of times you wake up, and it shortens the deep sleep stages your body needs for recovery. If that happens, try dropping to a 10.5 tog or keeping a window cracked.
What Does 15 Tog Mean?
A 15 tog duvet is the warmest standard rating available in the UK. It is designed for very cold bedrooms, typically below 12C, or for people who sleep cold year-round. You will not find many 15 tog duvets in physical shops because the demand is niche, but they are available online from brands like Snuggledown and John Lewis.
Most UK sleepers do not need a 15 tog duvet. Central heating keeps most bedrooms above 14C even in January, and a 13.5 tog duvet handles that comfortably. The exception is uninsulated bedrooms, loft conversions with poor draught-proofing, or anyone who genuinely feels cold under a 13.5 tog. If that sounds like you, a 15 tog duvet or a thick weighted blanket layered over a 10.5 tog might be the answer.
Frequently Asked Questions
What tog duvet is best for summer in the UK?
A 4.5 tog duvet is the standard summer pick. It traps enough warmth for open-window nights without overheating, and it pairs well with a light sheet when temperatures stay above 15C. The Utopia Bedding 4.5 Tog King is a popular budget option with OEKO-TEX certification.
What tog duvet is best for winter?
Most UK bedrooms suit a 13.5 tog duvet through winter. If your room drops below 14C or you sleep cold, a 15 tog duvet or an all-seasons combi set that clips two layers together gives extra warmth. The Silentnight So Snug 13.5 Tog is a widely available hollowfibre option.
Can I use two duvets together for more warmth?
Yes, and that is exactly how all-seasons duvets work. Two separate duvets (usually 4.5 tog and 9 tog) clip together with press studs to form a 13.5 tog layer. The Slumberdown All Seasons King ships this way. You can also stack two different duvets from your own collection, though the combined tog rating will not be exact.
Does tog rating affect sleep quality?
Overheating is one of the most common sleep disruptors. A tog that is too high for the room temperature pushes your body temperature up, which increases night waking and reduces deep sleep. Matching the tog to the season and your personal temperature helps you stay asleep longer.
How often should I replace my duvet?
Most duvets lose their loft and warmth after three to five years. If yours looks flat, clumps when you shake it, or no longer feels as warm as it used to, it is time for a replacement.
The Bottom Line
Tog ratings are not complicated, and they do not need to be. A 4.5 tog duvet handles summer, a 9 tog covers spring and autumn, and a 13.5 tog gets you through winter. If you want one purchase that covers all three seasons, an all-seasons combi set with a 4.5 tog and 9 tog that clips together is the most practical option for most UK bedrooms. The Slumberdown All Seasons King does exactly this, and it regularly comes in under forty pounds.
The room temperature you actually sleep in matters more than any number on a label. Use the tog rating as a starting point, then adjust based on how you feel. If you wake up sweating, drop a level. If you wake up cold, add a layer. For more help picking the right duvet, our duvet buying guide covers fill types, sizes and care.
For more sleep guides, visit SleepReview.
