I’m going to be honest here – I’ve been buying duvets based on their toggage (?) for years without actually knowing what “tog” really means.
Like most of us, I have a vague idea that it’s got something to do with how warm and thick the blanket’s going to be, but I have no idea how the process really works (it’s a bit like the “shag” of a carpet).
So, with the colder weather creeping in, I thought I’d finally find out what those three letters stand for, how they work, and what’s the best for the chillier months.
What does tog mean?
According to IKEA, “TOG stands for ‘Thermal Overall Grade’, which is a unit of measurement used to calculate the thermal insulation of a product, usually in the textile industry.”
However, that may be a backronym (using the letters of a word to stand for other words after the name has already been given, to explain its origin).
The name was given by Manchester scientists F. T. Peirce and W. H. Rees in 1946, when they created a new method of measuring the warming properties of fabrics which used to be expressed as m2⋅K/W.
Their paper doesn’t seem to use the initials IKEA refers to – it reads, “So that practical clothing may be described conveniently by a range of small integers, the unit of thermal resistance, to be called the “tog”, is the resistance that will maintain a temperature difference of 0.1°C. with a flux of 1 watt per square metre, or in more practical terms, 10°C. with a flux of 1 watt per square decimetre.”
The US version is called the Clo, and is about 1.55 tog.
However, IKEA is right to say: “Basically the higher the TOG, the warmer the product.”
It doesn’t make your bedding heavier or higher quality; it just means its thermal resistance (essentially heat retention) is better than a lower-tog option.
So what’s the best tog for a winter duvet?
Bedding company Linens Limited says anything above a 10 is a good tog for winter.
You can get duvets with a tog as high as 15 if you’re absolutely freezing at night, but many manufacturers stop at 13.5.
For the summer months, you can go as low as 4.5.
Of course, you can always get two 5-tog duvets and place them in the cover for winter, packing one away when it gets hot out (I’ve been doing this for years and will never look back).
However you manage the chill, though, at least you’ll know what a tog actually *is* now...