TOG is a unit of thermal resistance that tells you how warm a baby sleep bag is: the higher the number, the warmer the bag. For an air-conditioned nursery kept at 20–24°C, where most Bangkok families sit overnight, a 1.0 TOG sleep bag with one light layer underneath is the standard choice. Below 20°C, move to 2.5 TOG. Above 24°C, use 0.2–0.5 TOG or a single cotton layer.
Key takeaways
• 1 tog = 0.1 m²·K/W. It is a measured fabric property, defined in the UK and tested under British Standard BS 4745.
• Match the TOG to the actual room temperature at cot level, not to the season and not to the number on the AC remote.
• A typical Thai air-conditioned nursery (20–26°C) needs 0.2–1.0 TOG. The 2.5 TOG "all-season" bag sold in the UK is usually too warm here.
• Check the chest or back of the neck, not the hands and feet. Never add a blanket over a sleep bag.
What does TOG actually mean?
TOG stands for Thermal Overall Grade. It is a unit of thermal resistance how much a fabric slows heat passing through it, developed at the Shirley Institute in Manchester in the 1940s, and 1 tog is defined as 0.1 m²·K/W. In the UK, the tog value of textiles is measured on a "togmeter" under British Standard BS 4745:2005. It is the same unit used for duvets.
In everyday terms: 0.2 TOG is a single layer of light fabric with no filling; 1.0 TOG is a lightly padded bag; 2.5 TOG is a winter-weight bag for heated homes in cool climates; 3.5 TOG is for cold, unheated rooms. The number describes the bag only — what your baby wears underneath adds warmth on top of it.
Why the "ideal" nursery temperature is different in Thailand
Almost every TOG guide online is written for the UK, Europe or North America, where a heated bedroom at 16–20°C is normal. That is why so many imported sleep bags are 2.5 TOG.
Thailand is the opposite case. A Bangkok bedroom without air-conditioning sits well above 24°C at night for most of the year. With air-conditioning, most families set 24–26°C — the Ministry of Energy and EGAT actively promote 26°C to save electricity — and many parents cool the nursery a little further to 22–24°C for sleep. That puts the typical Thai nursery squarely in the 1.0 TOG band, occasionally the 0.2–0.5 band, and almost never in the 2.5 TOG band unless the AC runs at or below 20°C all night.
Two practical points. First, put a room thermometer next to the cot and use its reading, not the number on the AC remote: the air at cot level is often warmer than the set-point, especially in rooms with a high ceiling or an AC unit far from the cot. Second, choose your TOG for the temperature during the coldest part of the night (typically 2–5 a.m., when the AC has been running longest), and adjust what baby wears underneath rather than swapping bags.
TOG chart: which sleep bag for which room temperature?
Why the "ideal" nursery temperature is different in Thailand
Almost every TOG guide online is written for the UK, Europe or North America, where a heated bedroom at 16–20°C is normal. That is why so many imported sleep bags are 2.5 TOG.
Thailand is the opposite case. A Bangkok bedroom without air-conditioning sits well above 24°C at night for most of the year. With air-conditioning, most families set 24–26°C — the Ministry of Energy and EGAT actively promote 26°C to save electricity — and many parents cool the nursery a little further to 22–24°C for sleep. That puts the typical Thai nursery squarely in the 1.0 TOG band, occasionally the 0.2–0.5 band, and almost never in the 2.5 TOG band unless the AC runs at or below 20°C all night.
Two practical points. First, put a room thermometer next to the cot and use its reading, not the number on the AC remote: the air at cot level is often warmer than the set-point, especially in rooms with a high ceiling or an AC unit far from the cot. Second, choose your TOG for the temperature during the coldest part of the night (typically 2–5 a.m., when the AC has been running longest), and adjust what baby wears underneath rather than swapping bags.
What should a baby wear under a 1.0 TOG sleep bag?
Never put a blanket over a sleep bag. The American Academy of Pediatrics prefers layers of clothing or a wearable blanket to loose blankets, because loose bedding can cover the face or trap the baby.
How do I check my baby isn't too hot or too cold?
• Feel the chest, tummy or the back of the neck. Warm and dry means the layering is right.
• Cool hands and feet are normal and are not a sign that baby needs another layer
• Signs of overheating: sweating, damp hair, flushed cheeks, clammy skin, rapid breathing. Remove a layer straight away.
• If the room sits between two TOG bands, choose the lighter bag and add a layer underneath. A slightly cool baby wakes and tells you; an overheated baby is a safety risk.
Sleep bag safety checklist
• Fitted at the neck and armholes so the head cannot slip down inside the bag.
• Correct size for age and weight — do not buy a size up to "grow into".
• No hood. Arms free once your baby shows signs of rolling; stop swaddling at that point.
• Baby on their back, on a firm flat mattress, with nothing else in the cot — no blankets, pillows, bumpers or soft toys.
• Zip fully closed and the neck check done every time you put baby down.
The Petit Pie Sleep Bag — Cirque Pastel, 1.0 TOG
We designed our sleep bag for the room most of our customers actually have: an air-conditioned Bangkok nursery at 20–24°C. It is rated 1.0 TOG, so it is the one bag you need year-round in an air-conditioned room, and you adjust warmth with the bodysuit underneath.
Fit note: if your baby is at the top of a size, choose the size that fits at the neck and armholes today, not the next one up.
Frequently asked questions
Q: What does TOG mean on a baby sleep bag?
A: TOG (Thermal Overall Grade) is a unit of thermal resistance: 1 tog = 0.1 m²·K/W. The higher the TOG, the warmer the sleep bag. It is measured under British Standard BS 4745 and is the same unit used for duvets.
Q: Which TOG sleep bag do I need for an air-conditioned room at 25°C?
A: 25°C is at the top of the 1.0 TOG band. Use a 1.0 TOG bag with a nappy or a short-sleeve bodysuit underneath. If your baby is sweaty at the back of the neck, drop to a 0.2–0.5 TOG bag.
Q: Can my baby use a 1.0 TOG sleep bag all year round in Thailand?
A: Yes, if the room is air-conditioned to 20–24°C. Change only the layer underneath as the temperature moves. In a room without air-conditioning (usually above 26°C) use a 0.2–0.5 TOG bag or a single light layer instead.
Q: Is a 2.5 TOG sleep bag too warm for Thailand?
A: Usually, yes. 2.5 TOG is designed for 16–20°C rooms, which is a heated winter bedroom in the UK or Europe. In Thailand it only makes sense if the AC runs at or below 20°C all night.
Q: What should my baby wear under a sleep bag?
A: One light layer: a short-sleeve bodysuit at 22–24°C, a long-sleeve bodysuit at 20–22°C, nappy only above 24°C. No more than one layer more than an adult would wear to be comfortable in the same room.
Q: Can I put a blanket over a sleep bag?
A: No. A sleep bag replaces the blanket. No extra bedding is needed with a sleeping bag, and loose blankets in the cot increase the risk of overheating and face covering.
Q: When can my baby start using a sleep bag, and when should I stop swaddling?
A: A sleep bag can be used from newborn as long as it fits properly at the neck and armholes. Stopping swaddling as soon as the baby shows signs of trying to roll; an arms-free sleep bag is the safe next step. Petit Pie sizes start at 3–6 months.
Q: Is 1.0 TOG the same across brands?
A: The unit is the same, but every product is measured separately and fabrics differ, so treat brand charts as a guide rather than a guarantee. Always check your baby's chest or neck rather than relying on the number alone.
