Tog ratings explained: Get the right duvet for you

Buying a duvet can be a bit of a conundrum when there’s so much choice, especially with numerous tog ratings available. While you’ve no doubt heard of the term tog rating, you may not entirely be sure what it means – or what impact buying the wrong one can have on your sleep quality.

“Being too hot or too cold can lead to disrupted sleep; by selecting the right tog rating for your duvet, your body temperature is more likely to stay regulated and therefore more conducive to a good night’s rest,” says Jessica Hanley, founder at Piglet in Bed.

But what is the right tog rating for you? We ask the experts what a tog rating actually is; how it’s measured; why your duvet might not even have a tog rating; and which is best for each season and for you personally.

Tog ratings explained: What you need to know

What is a tog rating?

The tog rating system was created to describe the thermal resistance of a product, i.e. how effectively it traps heat. It was introduced as an easy way for consumers to gauge how warm a product is, with the higher the tog, the warmer the product. While many of us are familiar with tog rating when it comes to duvets, it’s also used for sleeping bags, baby sleep sacks, carpet underlay and even thermal socks.

How is a tog rating measured?

The tog scale generally runs from a very cool 1 tog to 15 tog for a super toasty duvet, although there are some 18 togs available for very chilly households. The product is given its rating based on a calculation done in a lab rather than a real-life scenario, so it’s worth considering that there are other factors at play that will influence how cosy your duvet feels in reality. For example, a duvet’s tog rating doesn’t necessarily indicate thickness – a puffy, cloud-like down duvet might have the same tog as a thin fleece design, such as Simba’s Hybrid duvet. The filling type and outer-casing material may also affect your temperature – for example, synthetic materials can make some hot under the collar, while those with moisture-wicking properties, such as cotton, may make them feel cooler.

Why doesn’t my duvet have a tog rating?

While the tog rating is the most common way to determine a duvet’s warmth, there are a few exceptions. “Wool duvets aren’t officially weighted by tog, as wool is naturally thermoregulating and maintains your body temperature throughout the night,” explains Jessica. More often than not, wool duvets will instead be given light, medium and warm ratings, with the first being equivalent to around a 4-6 tog, ideal for summer, a medium duvet at around 7-10 tog, equivalent to an all-round duvet, and lastly a warm, 11-14 tog, just right for a winter duvet. While these can vary, usually the company will clearly provide a tog equivalent to make it easy to select the right one for you.

It’s not just wool duvets that don’t have a tog rating – silk duvets are measured by the gram weight per square metre (gsm), and the heavier the material, the warmer it will be. Some down-like alternative duvets and those with innovative non-natural fillings may also be given a light or warm rating, much like wool duvets, due to not being compatible with the tog testing machine.

Summer versus winter tog ratings

“As a general rule of thumb, 4.5 or less is perfect for summer, 7-9 is suited to milder spring and autumn weather while 10.5 upwards is great for winter months, or for those of us who like an extra bit of warmth at night,” reveals Georgia Metcalfe, founder of French Bedroom. An all-seasons duvet can be a good investment, which allows you to fasten together two duvets (usually a summer and mid-weight tog) to create one warmer duvet for the chillier winter months. If you usually sit somewhere between a summer or winter duvet, one all-round duvet (usually a 7-9 tog) may see you through the whole year.

While a lot of it comes down to personal preference and whether you’re a hot or cold sleeper, as a general rule of thumb, you’ll find that a 4.5 tog is best for keeping you cool and comfortable in summer and a 13.5 tog is ideal for winter, unless you sleep hot, in which case a 10.5 tog will prevent overheating.

What tog rating is best for a toddler or child?

“As children have smaller bodies, a duvet will trap more air around them and keep them warmer at a lower tog rating,” explains Emily Attwood, co-founder of Scooms. Emily suggests that toddlers and children under the age of 10, should use a lightweight, single-size 2.5 or 4.5 tog duvet throughout the year. If they feel chilly, then the addition of a light blanket is preferable to swapping to a higher tog duvet; for children, duvets are available up to 7 tog for the winter months if your house is like a freezer.

“Babies under 12 months are too young for duvets due to the risk of overheating, so if your child is under this age, you need to ensure they sleep under a blanket or in a sleeping bag specifically designed for their age,” adds Emily. The recommended tog rating for baby sleeping bags according to Snüz is 2.5 tog for year-round use for room temperatures between 16-20 degrees, while a 1 tog is recommended for warmer summer months, when the temperature is between 21-23 degrees.

Which is the best tog rating for me and why?

Although the tog rating plays a large part in the warmth a duvet provides, the materials and filling also have a crucial role. Attwood points out that a duvet with a high fill power will be more effective at keeping you warm, so the higher the fill power, the toastier you’ll be. Conversely, a higher fill weight doesn’t mean it will be warmer, just heavier. The material is also important – fillings and outer casings made from natural materials tend to be more breathable, such as down, wool, silk and cotton, while those with synthetic materials such as polyester can make a duvet feel hotter, so look for those that offer cooling or temperature regulating technology.

Environmental and personal factors will also have an impact on whether you go for a higher or lower tog duvet. For example, Dr Greg Potter, PhD and Sleep Expert at The Fine Bedding Company, points out that women going through menopause or those who have certain skin conditions, such as eczema, which may be aggravated by heat will probably need to choose a lower tog rating all year round in order to keep their temperature down and have a comfortable night’s sleep. If you live in a cold climate or your bedroom tends to feel chilly at night (sub 16 degrees celsius), then you’ll probably want to up the tog rating to ensure that you’re sufficiently warm.

Regardless of all these variables, the best value and most popular option tends to be an all-seasons duvet, made up for a 4.5 tog for summer and 9 tog for in-between months, that then fastens together to make a 13.5 tog in the chillier winter months, covering all bases.