Some baby sleep bags have 'Tog' ratings on them, from 0.1 to 3.5. Obviously, it's some kind of warmth rating, but what do the numbers actually mean?
Even more confusingly, when you buy doonas, you'll see Tog ratings from 1.5 all the way up to 15.
So why the difference? Basically, Tog is a measure of thermal resistance or thermal insulation, or how warm the doona or sleeping bag is.
Doonas (or duvets, as they're known in England where the Tog rating originates) are generally sold with different Tog ratings, according to how warm the weather, or the room is. As a guide:
- 4.5 tog - Lightweight summer duvet
- 9.0 - 10.5 tog – Spring/autumn duvet
- 12.0 - 13.5 tog – winter weight duvet
Baby sleeping bags, however, have different Tog ratings.
- 0.5 tog = for hot weather / warm nursery 24-27 degrees
- 1.0 Tog = for autumn/spring weather in temperatures of 20-24 degrees
- 2.5 - 3.5 Tog = ideal for cooler nursery temperatures of 16-20 degrees
You'll also need to dress baby appropriately under that sleeping bag. So in cooler temperatures, you're going to need a singlet, and warm pyjamas under that sleep bag, while in warmer temperatures you'll need cooler pyjamas. All those extra layers add up to extra Togs, or thermal insulation. And on really hot nights, your baby will probably just be wearing a nappy and a singlet under a cool sleep bag, which means a lower Tog.
Nerd alert! Here's a fun fact: the word TOG is short for Shirley Togmetre, which is the actual name for the measurement. The British Cotton Industry Research Association in Manchester, England, was known as the Shirley Institute and it was they who came up with the TOG rating. So next time you're shopping for doonas, or baby sleep bags, you can stroke your chin knowledgeably and say, "I believe this rates a 1.5 on the Shirley Togmetre." Or not, of course. Entirely up to you.
And don't ask me who Shirley was. I don't know.
Image credit: Dimbledar on Flickr
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