Baby Sleep Tog Guide UK 2026: The NHS-Aligned Lullaby Trust Temperature Chart

The Lullaby Trust safer-sleep guidance (last reviewed 28 February 2026) recommends a 16-20C bedroom for babies and a tog-matched sleep bag. Babies are safer cooler than too hot – and the chest-or-back-of-neck check beats any rigid chart.

It is 11pm. You are standing over the cot, a 1.0 tog and a 2.5 tog sleep bag in hand, wondering which is right for tonight’s 19°C bedroom. The honest answer is that there is no single, perfect chart that applies to every baby in every home. However, there is a clear, UK-aligned framework based on the Lullaby Trust’s safer-sleep guidance, which is endorsed by NHS health visitors and midwives across the country.

Their advice, last reviewed in February 2026, provides a reliable foundation. The core principle is simple: babies are safer being cooler than being too hot. This guide will walk you through the recommended room temperature, a working tog chart, how to check your baby’s temperature, the essential safety rules, and what to do in UK summer and winter.

The Lullaby Trust 16-20°C rule and why it matters

The Lullaby Trust, the UK’s leading safer-sleep charity, recommends that a baby’s room temperature be maintained between 16 and 20°C. This specific range is the cornerstone of their guidance because of the established link between overheating and an increased risk of Sudden Infant Death Syndrome (SIDS). As they state directly, babies are safer being cooler than being too hot.

It can be difficult to judge a room’s temperature by feel alone, especially when you are tired; many UK bedrooms feel cooler than they actually are. Therefore, using a simple room thermometer in the rooms where your baby sleeps is a practical first step. This guidance was last reviewed on 28 February 2026, making it current for use in May 2026. NHS health visitors and midwives align their advice with this standard, so getting the room temperature right is the essential first layer of your baby’s sleep clothing strategy.

What is a tog and why no UK chart is ever perfectly accurate

A tog is a unit of measurement for thermal insulation, used to indicate how warm a product like a sleep bag or blanket will be. The higher the tog rating, the warmer the item. They typically range from 0.2 tog, designed for very hot weather, up to 3.5 tog for cold conditions. It is a useful system, but the Lullaby Trust explicitly states it cannot publish a strict, universal chart matching togs to room temperatures.

There are three main reasons for this. First, every product is made from different materials and different percentages of those materials, affecting breathability and warmth. Second, the heat trapped between layers of clothing and bedding changes the overall insulation significantly. Third, and most importantly, every baby is different; some naturally run warmer than others. Therefore, any tog-versus-temperature chart, including the working guide provided here, must be treated as a helpful starting point, not a fixed rule. The non-negotiable final step is always to check your baby’s actual temperature.

The working UK tog chart (guide, not gospel)

The following chart is a commonly used manufacturer-standard guide. It is a starting point for a healthy, full-term baby in a well-ventilated room. You must adjust based on your baby’s individual response and the chest-and-neck check.

How to actually check baby is the right temperature (the chest-and-neck method)

This is the method used and recommended by UK health visitors, as per Lullaby Trust guidance. After your baby has been asleep for about 20 to 30 minutes, place your hand on their chest or the back of their neck. Do not use their hands or feet to judge their temperature. It is completely normal for a baby’s hands and feet to feel cooler than their core; this is due to their less developed peripheral circulation and is not a sign that they are cold.

If the chest or neck feels hot or sweaty, your baby is too warm; remove a layer of clothing or use a lower tog sleep bag. If the chest feels cool or cold, add a layer of clothing or switch to a higher tog bag. New parents often overdress their baby because they themselves feel chilly. A baby generally needs the same or fewer layers than an adult to be comfortable at the same room temperature.

The absolute do-nots (the rules that prevent accidents)

The Lullaby Trust’s safety rules are clear and must be followed to reduce risk. These are not suggestions; they are evidence-based directives designed to prevent SIDS and sleep-related accidents.

UK summer hot-weather practical plan

During a UK heatwave, keeping the room below 20°C can be a challenge. Close curtains or blinds during the day to prevent the sun from heating the room. In the evening, open the bedroom door and a window to encourage air flow, if it is safe to do so. You can use a fan to cool the room, but never point it directly at the baby. Use your room thermometer to monitor the actual temperature; do not guess based on how it feels outside.

In very hot weather where the room remains above 24°C, even after taking these steps, a short-sleeve vest or just a nappy is perfectly safe for sleep. You may use a very light 0.5 tog sleep bag or no sleep bag at all. Hot UK nights are when most overheating accidents occur, as parents may add layers thinking the night is cool, while the bedroom retains daytime heat. Trust the thermometer, and check your baby’s chest more frequently.

UK winter cold-weather practical plan

If you struggle to keep the room above 16°C in winter, the advice is to add layers of clothing, not more bedding. Use a higher tog sleep bag, such as a 3.5 tog. Dress your baby in a long-sleeve baby grow over a long-sleeve vest, and add socks if needed. Never use a hat indoors. Never place a hot water bottle or an electric blanket in the cot with your baby.

A common winter mistake is to use a high-tog sleep bag and then add extra blankets on top; this combination significantly increases the risk of overheating. Ensure the sleep bag fits snugly around your baby’s neck and shoulders so they cannot wriggle down inside. After 20 to 30 minutes of sleep, check their chest. The room may feel cold, but a baby in a correctly layered 3.5 tog sleep bag will often be the right temperature or even warm to the touch.

Sleep bag sizing, brands and the BS EN 16781:2018 safety standard

Baby sleep bags in the UK are typically sized by a combination of your baby’s weight and age band, not by age alone. Common size brackets are 0-6 months (often with a weight limit around 8.2 kg), 6-18 months, and 18-36 months. Always check the specific manufacturer’s size guide. The bag must fit snugly around the neck and armholes to prevent your baby from slipping down inside.

The key safety feature to look for on any product is the British Safety Standard mark: BS EN 16781:2018. This is the UK standard for the safety of children’s sleep bags. Several reputable UK brands design their products to meet this standard, including Tommee Tippee Grobag, ergoPouch, The Gro Company, JoJo Maman Bebe, Mamas and Papas Dreampod, Slumbersac, MORI, Aden + Anais, and Love To Dream. The Lullaby Trust does not endorse specific brands, so it is your responsibility to check for the standard on the label.

Frequently Asked Questions

What tog sleep bag should I use at 19°C?

For a 19°C room, a 1.0 tog or 2.5 tog sleep bag is typically suitable. If your baby wears a long-sleeve baby grow underneath, a 1.0 tog may be enough. If they are in a short-sleeve vest only, a 2.5 tog might be better. The final decision rests on checking your baby’s chest after 20-30 minutes of sleep. If it feels hot or sweaty, choose the lighter option; if it feels cool, choose the warmer one.

Can my baby overheat in a sleep bag?

Yes. Overheating is a significant risk factor for SIDS. It can happen if the room is too warm, the tog rating is too high for the conditions, extra blankets are added on top of the sleep bag, a hat is left on indoors, or sleep bags are doubled up. Always use a room thermometer and perform the chest-and-neck check to ensure your baby is not too hot.

Why does the Lullaby Trust not give an exact tog chart?

Because the materials and construction of every product differ, the warmth created by trapped air between layers is unpredictable, and every baby’s metabolism is unique. Any rigid chart would be misleading. The Lullaby Trust’s position, last reviewed in February 2026, is that a room thermometer combined with the hands-on chest check is a more reliable method than any fixed chart.

Are weighted baby sleep bags safe in the UK?

No. The Lullaby Trust does not recommend weighted swaddles, sleep bags, or blankets for babies under one year. The added weight poses risks of overheating, accidental head covering, and can restrict a baby’s chest movement and breathing. This advice applies to all brands and products.

What if my baby’s hands feel cold – do I add a layer?

No. Cool hands and feet are normal for babies due to their circulatory system. They are not an accurate indicator of your baby’s core temperature. Rely on feeling their chest or the back of their neck. Only add a layer if the chest itself feels cold to the touch.

Can I use a sleep bag if my baby has a temperature or fever?

Yes, but do not add extra layers because your baby feels hot. Dress them for the room temperature as you normally would. Overbundling a feverish baby can prevent heat from escaping. If your baby has a fever and is under 6 months old, contact NHS 111 or your GP urgently. The Lullaby Trust Baby Check app can help assess symptoms.

When can my baby start using a duvet or pillow?

The NHS and Lullaby Trust advise no pillows, duvets, or thick bedding in a baby’s sleep space until they are at least 12 months old. A sleep bag is the safer alternative for the first year. After their first birthday, you can gradually introduce a low-tog duvet and a small, flat pillow if you wish, as part of the move to a toddler bed.

This article is informational only and does not replace personalised advice from your GP, pharmacist, or another qualified healthcare professional.