TOG is a unit of measurement for the insulation and warmth of sleepwear and bedding.
Put simply, the lower the TOG rating, the lighter and cooler the fabric is. The higher the rating, the more padded and insulated it is for warmth.
The reason you would choose TOG rated sleepwear for your child is to avoid overheating and to keep their body at a more consistent temperature while their ability to regulate it themselves is still developing.
There is different TOG ratings for cool and warm room temperatures. You would choose the most suitable TOG based on the room your child is sleeping in.
TOG RATINGS & ROOM TEMP;
0.2 TOG 24°C+
0.3 TOG 24°C+
1.0 TOG 21 - 24°C+
2.5 TOG 17 - 23°C+
3.5 TOG 14 - 21°C+