Is a higher TOG always warmer?

Yes, but it is not automatically safer. Match the TOG to the room temperature and check the baby's neck rather than adding layers.

Do babies need a sleep bag?

No. A well-fitting sleepsuit is enough. If you use a bag, it must fit the neck and armholes so it cannot slip up over the face.

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TOG ratings and room temperature: what to dress a baby in

TOG (thermal overall grade) measures how warm a sleepsuit or sleep bag is. Higher numbers trap more heat. The chart below is the range most brands publish; always check the brand's own chart for the specific product.

Room temperature	TOG	Typical outfit
27 °C / 80 °F and above	0.2–0.5	Short-sleeve bodysuit, muslin or light cotton
24–27 °C / 75–80 °F	0.5	Light cotton sleepsuit
21–24 °C / 70–75 °F	1.0	Long-sleeve cotton sleepsuit
18–21 °C / 65–70 °F	1.5–2.5	Sleepsuit plus a 1.0–2.5 TOG bag
16–18 °C / 60–65 °F	2.5	Warmer sleepsuit plus a 2.5 TOG bag
Under 16 °C / 60 °F	3.5	3.5 TOG bag over a warm layer

Higher is not automatically safer

Overheating is a risk, so the aim is to match the room, not to pile on warmth. Use a room thermometer, and check the back of the baby's neck: hot and sweaty means a layer too many; cool and mottled means add one. A sleep bag is optional — if you use one, it should fit the neck and armholes snugly.

What to look for when buying

A TOG number stated by the brand, not guessed from fabric thickness.
Two-way zips and poppers that make night changes easier.
Fitted cuffs and a neck opening that cannot ride up over the face.
Cotton or bamboo next to the skin; avoid loose trims inside.

General information, not medical advice. Follow the brand's TOG chart and your health visitor or pediatrician's guidance.