TOG is just a warmth rating — higher means cozier.
It measures how much warmth a sleep sack or blanket holds in. A warmer room usually calls for a lower TOG, and a cooler room for a higher one.
2.5 TOG for cooler rooms 1.0 TOG for average rooms 0.5 TOG for warm rooms Higher number, more warmth held in
Match the TOG to the room, then check the neck once your baby is settled. That's usually a good start.
The TOG for each room
Match it to the room, not the season. Brands vary a little, so your sack's own label wins over this table.
Why the app stops at 2.5 TOG
The makers' charts move to a 3.5 TOG sack below 16°C (61°F). The Lullaby Trust says a cooler room can take an extra layer of clothing or a warmer sleeping bag. Baby Layers takes the extra layer: below 18°C (64°F) it adds a sleepsuit under the 2.5 TOG sack instead.
At the warm end it goes a step lighter than the charts too: from 26°C (79°F), a short-sleeve bodysuit and no sack. A baby is safer slightly cool than too warm.
Only ever one
Never two sacks on top of each other, and no blanket over a sack. The sack is the whole of the bedding.