Glossary
TOG rating
A numeric scale describing how much warmth a sleep sack or blanket provides, used to match gear to room temperature.
TOG stands for thermal overall grade, a rating originally used for fabrics that sleepwear and sleep sack brands adopted to describe warmth. A low TOG, often around 0.5, is meant for warm rooms, while a higher TOG, often 2.5 and up, is meant for cooler rooms. The number lets you compare warmth across brands even when the fabric or fill looks different.
Choosing a TOG starts with your nursery's actual temperature rather than the season on the calendar, since heating, air conditioning and room location all change how warm a space really is. Many sleep sack lines publish a simple temperature-to-TOG chart, and layering guidance usually assumes a onesie or light pajamas underneath rather than heavy clothing plus a high-TOG sack.
A common mistake is choosing TOG based on outdoor weather instead of the nursery itself, or stacking a high-TOG sack over thick fleece pajamas, which can contribute to overheating, one of the factors safe sleep guidance asks parents to watch for. If a baby's chest feels hot or sweaty at night, that is usually a sign to size down in TOG rather than remove crib bedding to compensate.