Ever bought a “winter duvet” that left you sweating by 2am, or a “lightweight” one that had you reaching for an extra blanket by midnight? You’re not alone, and it’s rarely bad luck. The real culprit is usually a mismatch between the duvet’s TOG rating and what your room and body actually need. The calculator above takes the guesswork out of it — just tell it the season and how warm you usually sleep, and it’ll give you a straight answer.
Free tool
Duvet TOG Calculator
Answer two quick questions to find the right duvet warmth for you.
TOG measures how well a duvet traps heat, not its thread count or fill weight. Higher TOG means warmer. These are general guidelines — personal comfort can still vary.
So what exactly is TOG, anyway?
TOG stands for Thermal Overall Grade, and despite the technical-sounding name, it’s a fairly simple idea. It measures how well a duvet holds onto heat, on a scale that usually runs from around 2 (very light, barely-there warmth) up to 16 or higher (thick, heavy winter warmth). The higher the number, the warmer the duvet.
Here’s the part that trips a lot of people up: TOG has nothing to do with thread count, fill weight in grams, or how “fluffy” a duvet looks in the packaging. Two duvets can have wildly different thread counts and still carry the same TOG rating, because TOG is purely about insulation, not softness or fabric quality. A duvet’s TOG comes down to its filling and construction, whether that’s down, synthetic fiber, or a wool blend, and how that filling is designed to trap air.
Why the same TOG doesn’t feel the same to everyone
This is the detail most product labels leave out entirely. TOG ratings are really written for an “average” sleeper in an “average” room, and almost nobody is perfectly average. Someone who runs warm at night, kicks off blankets, or sleeps in a room with decent airflow will often feel too hot under a TOG rating that a colder sleeper finds just right in the exact same room. That’s exactly why the calculator above asks about both the season and your own sleeping tendencies, rather than just handing out a single “winter” or “summer” number and calling it done.
A rough seasonal guide, if you want the short version
For genuinely hot summer nights or an air-conditioned bedroom, something in the 3 to 4.5 TOG range tends to feel right for most people. Spring and autumn, when nights are mild but not cold, usually call for something in the 9 to 10.5 range, which is why 10.5 TOG duvets are the best-selling, most “all-purpose” option in most bedding stores. Winter without central heating typically needs 13.5 TOG or higher, while a heated bedroom in winter often only needs something closer to 10.5, since the room itself is already doing part of the work.
A mistake worth avoiding
One habit that quietly causes a lot of restless nights is buying a single heavy duvet and trying to make it work year-round, layering it with extra blankets in winter and kicking half of it off in summer. It works, technically, but it’s rarely comfortable, and it’s part of why so many people report inconsistent sleep quality across seasons. Many people who sleep better long-term end up rotating between two duvets, a lighter one for warmer months and a heavier one for winter, sometimes combining both for the coldest stretches. It costs a little more upfront but tends to pay off in actual sleep quality.
Frequently Asked Questions
Can I combine two duvets to get a higher TOG rating
Yes, and it’s a common practice for very cold winters. Combining a 4.5 TOG and a 9 TOG duvet gives you roughly 13.5 TOG of combined warmth, which is often more flexible than buying one heavy winter-only duvet.
Does a higher TOG rating always mean better quality
No. TOG only measures warmth, not the quality of the materials or construction. A well-made 4.5 TOG summer duvet isn’t lower quality than a 13.5 TOG winter one, it’s simply built for a different purpose.
What TOG rating is best for a baby or toddler's room?
Children’s bedding generally uses lower TOG ratings than adult bedding for safety and temperature regulation, and specific age-appropriate guidelines exist for nursery bedding. It’s worth checking dedicated infant bedding safety guidance rather than applying adult TOG ranges directly.