Tog (unit)
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The tog is a measure of thermal resistance, commonly used in the textile industry, and often seen quoted on, for example, duvets.
The Shirley Institute in Britain developed the tog as an easy-to-follow alternative to the SI unit of m2K/W. Launched in the 1960s, the Shirley Togmeter is the standard apparatus for rating thermal resistance of textiles, commonly known as the Tog Test.
A tog is 0.1 m2K/W. In other words, the thermal resistance in togs is equal to ten times the temperature difference (in °C) between the two surfaces of a material, when the flow of heat is equal to one watt per square metre.
According to British retailer John Lewis, tog guidelines for duvets are as follows:[1]
| Lightweight summer duvet: | 4.5 tog |
| Spring/Autumn weight duvet: | 9.0 - 10.5 tog |
| Winter weight duvet: | 12.0 - 13.5 tog |
Another unit of thermal resistance of textiles is the clo, equal to 1.55 togs (1 tog = 0.645 clo).[2]
