Short answer: TOG indicates the thermal insulation of a baby sleep bag, but it should not be used on its own to decide what a baby should wear for sleep. You also need the actual room temperature, the fit and design of the sleep bag, the clothes worn underneath, the baby’s age and health, and a simple comfort check at the chest or back of the neck. Safe-sleep guidance from major health authorities is consistent on the essentials: place baby on the back, use a firm flat sleep surface, keep the head uncovered, avoid loose bedding and prevent overheating.
Online charts that say “TOG = temperature = exact outfit” can be useful starting points, but they are often presented as universal rules. They are not. Recommendations depend on the product, fabric, construction and manufacturer instructions. The UK NHS gives practical examples — including a 1.0 TOG sleep bag for rooms around 20 to 24°C — while the American Academy of Pediatrics (AAP) notes that research does not provide one precise overheating threshold that applies to every infant. The safest approach is therefore to combine the product instructions, a room thermometer and observation of the baby.
This guide explains how to choose a TOG without over-dressing, how to interpret room temperature and how to recognise situations in which clothing should be adjusted or medical advice is needed. If your baby was premature, had a low birth weight, is unwell or has a medical condition affecting temperature regulation, follow the individual advice from your healthcare team.
What does TOG mean on a baby sleep bag?
TOG stands for Thermal Overall Grade. It is a measure of thermal insulation: the higher the TOG value, the more heat the product is designed to retain. A light sleep bag around 0.5 or 1.0 TOG is therefore intended for warmer conditions than a 2.5 or 3.0 TOG product.
TOG does not measure your baby’s body temperature and does not tell you the room temperature. It also cannot, by itself, specify exactly how many layers of clothing should be worn underneath. Two sleep bags with the same TOG can differ in fabric, ventilation, cut, lining and construction. For practical dressing decisions, the chart or instructions provided for the exact sleep bag remain important.
In Europe, safety standards for children’s sleep bags address product design and testing. NF EN 16781 covers sleep bags intended for use in a child’s cot. Compliance with a product safety standard is useful information, but it does not turn a TOG value into a medical prescription or guarantee that overheating cannot occur.
TOG, room temperature and clothing: how to think rather than follow a chart blindly
| Room temperature | Common sleep-bag reference | How to use the information |
|---|---|---|
| About 16–20°C | A warmer sleep bag; the NHS cites 2.5 TOG for 16–20°C. | Start with the manufacturer’s chart, then check the baby’s chest or neck. |
| About 20–24°C | The NHS cites 1.0 TOG as a practical reference. | Adjust clothing underneath rather than adding a loose blanket. |
| About 24–27°C | The NHS cites 0.5 TOG. | Use very light clothing and watch carefully for signs of overheating. |
| Warmer than this | No single TOG number is enough. | Prioritise cooling the room, reducing clothing and following local heat guidance. |
This table is a reference, not a universal protocol. The NHS publishes these ranges to help families choose sleep bags. French public-health guidance focuses more broadly on avoiding an overheated room — commonly around 18–20°C — and using a sleep bag suited to the baby’s size and the season. If a flat remains at 23°C in midwinter, the measured temperature matters more than the word “winter” on the packaging.
Why the actual room temperature matters more than the season
A bedroom can remain at 23°C in December, while another can drop to 18°C in spring. Choosing only an “summer” or “winter” sleep bag therefore creates unnecessary uncertainty. Use a room thermometer and place it away from a radiator, direct sunlight, an open window or another location that could distort the reading.
The temperature can also change overnight. Heating schedules, building insulation and ventilation may all alter the room. You do not need to wake a sleeping baby hourly to check, but looking at the room temperature at bedtime and again when you wake for a feed can help if the home changes substantially during the night.
How can you tell if a baby is too warm?
Hands and feet are often cooler than the trunk and should not be used as the only guide. The NHS advises checking the baby’s tummy; other guidance suggests the chest or back of the neck. If the trunk feels very hot, the baby is sweating, has flushed skin or feels unusually warm, remove a layer and review the room temperature.
The AAP lists sweating, flushed skin and a hot chest among practical signs of overheating. It also recommends leaving the head uncovered during normal indoor sleep and avoiding hats, except in specific medical or immediate post-birth circumstances.
A baby who is very hot, difficult to wake, breathing abnormally or has a fever should not simply be “undressed and watched”. Measure the baby’s temperature using the recommended method and seek medical advice appropriate to the baby’s age and symptoms.
What if the baby feels cold?
Cool hands do not necessarily mean the baby is cold. Check the chest or back of the neck instead. If the trunk is cool and the room temperature is low, add one light layer of clothing or move to a more suitable sleep bag according to the manufacturer’s instructions rather than placing a loose blanket over the baby.
This is one of the main practical advantages of a correctly fitted sleep bag: it can provide warmth without a loose blanket moving towards the face. The AAP and other safe-sleep authorities prefer appropriate sleep clothing or wearable blankets to loose bedding for infants.
Fit matters as much as TOG
A sleep bag that is too large can allow the head or shoulders to slip down inside. A bag that is too small can restrict movement, pull on the shoulders or no longer suit the baby’s development. Always check the manufacturer’s height, weight and age guidance rather than choosing by age label alone.
The neck opening and armholes should be secure enough that the baby cannot slide into the bag. The NHS advises choosing a sleep bag that fits well around the shoulders. Before using a new sleep bag overnight, place it on the baby while awake and check that the zip works properly, the fabric cannot ride over the face and there is enough room for natural leg movement.
The lower part should allow the hips and knees to flex naturally. Avoid a bag that holds the legs tightly together or forces them straight.
What should a baby wear under a 1.0 TOG sleep bag?
There is no single outfit for every room. The NHS uses 1.0 TOG as a reference for rooms around 20–24°C; the clothing underneath should then be adjusted according to the exact temperature, the baby and the manufacturer’s chart. Near 20°C, some products may suggest a light sleepsuit. At 23–24°C, a lighter layer such as a bodysuit may be enough for some babies.
The Botanica 1.0 TOG baby sleep bag currently listed by Confort Enceinte is intended for approximately 0–6 months, with a stated baby length of 50–65 cm. Its product page describes prewashed 100% organic cotton muslin, a 1.0 TOG rating and declared compliance with NF EN 16781. These characteristics make it a lightweight sleep bag; they do not replace checking the real temperature of the room.
Can you put a blanket over a sleep bag?
As a general rule, do not add a loose blanket on top of a sleep bag to “increase” its TOG. The NHS advises adjusting clothing underneath the bag rather than adding blankets, and the AAP recommends keeping blankets, quilts, pillows and other soft objects out of an infant’s sleep area.
If the room is too cold for the sleep bag you have, a more predictable solution is to choose a different TOG or adjust the clothing underneath in line with the product instructions. Stacking improvised layers makes the total insulation harder to estimate.
Should a baby wear a hat to sleep indoors?
Not as part of a normal home sleep routine. The head should remain uncovered. The AAP advises against hats for routine infant sleep indoors, outside specific situations such as immediate post-birth care or neonatal treatment. Adding a hat because the baby’s hands feel cool can increase the risk of overheating.
Do cold hands need mittens?
Not simply because the hands feel cool. Some sleepsuits have fold-over mittens for scratching, but they should not be used as a temperature gauge. Check the trunk. If the baby’s chest is comfortable and the room is appropriate, cooler extremities are common.
TOG during a heatwave: what changes?
During very hot weather, the goal is not to find a “perfect TOG” but to reduce overheating. Ventilate the room when outdoor conditions are cooler and it is safe to do so, close shutters or curtains during strong sun, keep the cot away from direct sunlight and reduce clothing layers.
The NHS notes that in very warm weather babies may need very little sleep clothing. A 0.5 TOG bag is a common reference for rooms around 24–27°C, but if the room becomes even warmer the overall clothing needs to be reduced further. A fan can help move air around the room but should not be placed so that a strong stream blows continuously directly onto the baby.
An appropriate baby sleep and safety setup cannot compensate for an excessively hot bedroom. Measure the room and observe the baby.
TOG in winter: avoid the “more is always better” reflex
It is understandable to add a bodysuit, thick sleepsuit, socks, hat, warm sleep bag and blanket when it is cold outside, but this can create excessive insulation. In a bedroom maintained around 18–20°C, follow the sleep-bag manufacturer’s clothing chart and check the baby’s trunk after settling.
If the heating remains on overnight, measure the actual bedroom temperature instead of assuming the room is cold because it is winter. Avoid placing the cot next to a radiator, heater or direct warm-air flow.
Does a sleep bag replace the other safe-sleep rules?
No. Even with a correctly selected sleep bag:
- place baby on the back for every sleep;
- use a firm, flat mattress designed for the cot or bassinet;
- keep pillows, quilts, duvets, cot bumpers, soft toys and other loose items out of the sleep space;
- avoid inclined products or surfaces not intended for routine sleep;
- keep the baby’s face and head uncovered;
- follow local guidance on room-sharing with a separate infant sleep surface during the early months.
These principles matter more than achieving a theoretically “perfect” thermal setup. Our newborn sleep guide explains the wider safe-sleep environment; this article focuses specifically on thermal comfort and sleep bags.
Why weighted sleep bags should be avoided
The AAP is clear that weighted blankets, weighted swaddles and weighted sleep sacks should not be placed on or near a sleeping infant. Added weight over the chest or body is not part of a safe infant sleep strategy.
Do not confuse a thicker fabric or higher TOG with a weighted product. The concern is deliberate added weight intended to apply pressure.
Can a sleep bag also be used for swaddling?
Some products are designed to hold the arms in, while ordinary sleep bags leave the arms free. A standard sleep sack is not automatically a swaddling device. If a product has a swaddling function, follow the manufacturer’s age, weight and developmental limits closely.
As soon as a baby shows signs of attempting to roll, any product that restricts the arms should be reassessed and generally discontinued. A non-swaddling sleep bag that leaves the arms free can usually continue to be used as long as it fits correctly and is suitable for the baby’s size.
What does NF EN 16781 mean?
NF EN 16781 is the European safety standard for children’s sleep bags intended for use in a cot or similar sleep environment. It specifies safety requirements and test methods relating to product design and mechanical safety. It is not a universal thermal dressing chart and does not tell parents exactly what clothes to put under a sleep bag at every degree.
The Botanica sleep bag listed by Confort Enceinte states compliance with NF EN 16781 on its product page. That is useful product information and should be kept separate from public-health recommendations about sleep position, room temperature and keeping loose bedding out of the cot.
Does organic cotton determine the TOG?
No. TOG reflects the total insulation of the finished product, not simply the fibre name. Organic cotton may be chosen for material, feel or production reasons, but “cotton” alone does not tell you whether a sleep bag is warm or cool. Thickness, layers, filling, weave and construction all contribute.
Do not replace the TOG label with assumptions such as “cotton means summer” or “velour means winter”. Use the stated TOG and product instructions.
Why do TOG charts sometimes disagree?
Because not every chart comes from the same source and not every sleep bag is constructed the same way. One brand may suggest a short-sleeve bodysuit under 1.0 TOG at a given temperature while another suggests a light sleepsuit. That does not automatically mean that one chart is wrong.
Medical and public-health recommendations also avoid specifying a single outfit for every exact degree. The AAP notes that overheating is difficult to define precisely in research and instead advises avoiding excessive layers, keeping the head uncovered and watching practical signs such as sweating, flushing and a hot chest.
A simple decision tree before bedtime
- Measure the room. Do not base the decision on the outdoor weather.
- Read the product label. Check TOG, size and clothing guidance.
- Check the fit. The head should not be able to slip through the neck opening and the legs should have room to move.
- Choose a simple layer underneath. Avoid “just in case” piling of clothing.
- Place baby on the back in a clear cot. Do not add a loose blanket over the sleep bag.
- Check the chest or back of the neck. Remove or add one clothing layer if needed.
- Reassess if the room changes substantially. Heating, travel, a heatwave or illness can change the situation.
Travel, hotels and grandparents’ homes: TOG does not travel alone
A sleep bag that works perfectly at home may be too warm in a heavily heated hotel room or too light in a cooler house. A compact room thermometer and two simple clothing options can make travel decisions easier.
Check the sleep surface as well: firm flat mattress, properly fitted sheet and no pillows or loose bedding. A correct sleep bag cannot make an improvised sofa, adult bed or soft mattress a safe infant sleep environment.
What if the baby has a fever?
A baby with a fever does not generally need extra layers “to sweat it out”. Excess clothing can increase discomfort. Follow the advice of the healthcare professional and avoid sudden aggressive cooling.
In babies under 3 months, any fever requires urgent medical assessment. Do not try to manage a raised body temperature only by changing TOG. Room temperature and clothing affect comfort, but they do not treat the cause of fever.
When should you seek medical advice?
- your baby is under 3 months and has a fever: seek urgent medical advice;
- the baby is difficult to wake, breathing abnormally or unusually floppy;
- the baby sweats heavily despite light clothing and a moderate room temperature;
- your baby was premature or had a low birth weight and you are unsure how to dress for sleep;
- a medical condition or treatment affects temperature regulation;
- you remain worried despite an apparently appropriate sleep setup.
Frequently asked questions
What TOG for a room at 20°C?
The NHS cites 2.5 TOG for 16–20°C and 1.0 TOG for 20–24°C. At the 20°C boundary, use the chart for the exact product and adjust the layer underneath after checking the baby’s trunk.
What TOG for 22°C?
1.0 TOG is a common reference for 20–24°C. Still check the sleep-bag manufacturer’s instructions, the fit and the clothing underneath.
What TOG for 24°C?
The NHS uses 1.0 TOG for approximately 20–24°C and 0.5 TOG for 24–27°C. At 24°C, the product instructions and the baby’s actual comfort help you choose between those references.
Can you use a 1.0 TOG sleep bag in winter?
Yes, if the measured room temperature and clothing underneath match the product’s recommendations. The outdoor season is not enough information.
Can you use a 2.5 TOG sleep bag in summer?
Only if the room remains cool enough and the manufacturer’s guidance supports that setup. In a warm room, 2.5 TOG may provide too much insulation.
How do I know if my baby is too hot at night?
Check the chest or back of the neck. Sweating, a very hot chest or flushed skin are reasons to remove a layer and check the room.
Do cold hands mean my baby needs another layer?
No. Hands and feet can feel cool while the trunk is comfortable. Use the chest or neck rather than the hands alone.
Does a baby always need a bodysuit under a sleep bag?
No. It depends on the room temperature, TOG and the manufacturer’s clothing chart.
Can a baby wear a sleepsuit under a sleep bag?
Yes when the room temperature and product instructions support it. Avoid combining multiple heavy layers without a clear reason.
Should a baby wear socks in a sleep bag?
Not routinely. If the baby already wears a footed sleepsuit, socks add another layer. Use the trunk and room temperature to guide you.
Can you put a blanket over a sleep bag?
It is generally better not to. Adjust the clothing underneath or use an appropriate TOG. Safe-sleep guidance recommends keeping loose bedding out of the infant sleep space.
When can a baby start using a sleep bag?
From birth for products specifically designed for the newborn’s size and weight. The neck opening must prevent the baby from slipping inside.
When should you move to the next sleep-bag size?
When the baby reaches the manufacturer’s size or weight limit, the length becomes restrictive, or the neck and armholes no longer fit securely.
Is a sleep bag with sleeves warmer?
Often, but TOG and the manufacturer’s instructions provide better information than sleeves alone.
Are weighted sleep bags safe?
The AAP advises against weighted infant sleep products. Use a standard correctly fitted sleep bag instead.
Does TOG prevent SIDS or sudden unexpected infant death?
No. TOG is a product insulation rating, not a preventive medical device. Risk-reduction advice focuses on the overall safe-sleep environment: back sleeping, a firm flat surface, a clear cot, smoke-free surroundings and avoiding overheating, among other measures.
Key takeaways
- TOG measures the insulation of the sleep bag, not the baby’s body temperature.
- Measure the room and use the manufacturer’s chart for the exact product.
- The NHS uses 1.0 TOG as a practical reference for rooms around 20–24°C, but this is not a universal law.
- Check the chest or back of the neck rather than relying on cold hands.
- A sleep bag should fit securely around the shoulders and keep the head uncovered.
- Do not add loose blankets over a sleep bag; keep the cot clear.
- Avoid overheating, indoor hats and weighted sleep products.
The most useful question is therefore not “Which TOG for August?” but “What is the actual temperature of this room, what is the TOG and fit of this particular sleep bag, and how does my baby feel in this clothing?”. This method reduces rigid rules while keeping the focus on safe, observable decisions.
Sources
- Santé publique France — Sudden unexpected infant death / safe sleep recommendations (French), accessed 21 August 2026.
- NHS — Baby safer sleep advice, accessed 21 August 2026.
- NHS — How to dress a newborn baby, accessed 21 August 2026.
- American Academy of Pediatrics — Sleep-Related Infant Deaths: Updated 2022 Recommendations, Pediatrics, 2022.
- Can infant sleeping bags be recommended by medical professionals as protection against sudden infant death syndrome?, peer-reviewed literature review, 2019, PMID 30297442, DOI 10.1136/archdischild-2018-316093.
- Baby sleeping bag and conventional bedding conditions—comparative investigations by infrared thermography, peer-reviewed study, 2011, PMID 21630179, DOI 10.1055/s-0031-1277142.
- AFNOR — NF EN 16781: children’s sleep bags for use in a cot (French standard page).
- French National Health Insurance — Fever in children: what to do and when to seek medical care (French), accessed 21 August 2026.
General guidance does not replace individual medical advice. For a premature, low-birth-weight, unwell or medically vulnerable baby, follow the instructions from the healthcare team.
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