Room Temperature and What to Dress Baby In

The three answers

Search for the right room temperature for a baby and you will get one confident number. There are actually three, from three safe sleep authorities, and the differences are not rounding errors.

• The Lullaby Trust (UK): "The recommended room temperature for babies is 16 – 20°C." It recommends using a room thermometer, "as it can be difficult to guess temperature".
• The AAP (US): recommends avoiding overheating and head covering for infants and "temperatures between 68°F to 72°F for infants and children" — roughly 20 to 22°C, so its floor sits at the top of the UK range.
• Red Nose Australia: declines to give one. "There is no perfect temperature, and what is a safe temperature depends on many factors, including the season or how baby is dressed." It goes further on thermometers: "To date, there is no evidence showing that a specific room temperature prevents sudden unexpected death in infancy."

Two things to take from that. First, if your room sits at 21°C you are outside the UK recommendation and inside the American one, and neither body thinks that is dangerous. Second, all three agree on what overheating is: a real, established SIDS risk factor. They differ on how best to manage it, not on whether it matters.

What they all agree on

The check, and it is not the thermostat. Feel your baby's chest or the back of their neck. The Lullaby Trust: "your baby's hands and feet will usually be cooler, which is normal." If the skin is hot or sweaty, remove a layer. Red Nose describes the same test using the back or tummy and lists flushed cheeks and sweating as signs of heat stress.

They also agree on the direction of error. The Lullaby Trust states it directly: "Research shows that babies are safer being cooler than being too hot."

And on hats. No hats indoors, from every body. The Lullaby Trust explains why: babies maintain body temperature by releasing heat through their head, so covering it means they can overheat.

Why there is no official tog chart

This is the most useful thing on this page, and it is the thing the sleeping-bag industry does not tell you. Every tog chart you will find online comes from a company that sells sleeping bags. The Lullaby Trust has been asked for one repeatedly and publishes its refusal, with reasons:

• "Every product is made up of different materials, and different percentages of materials. The thermal insulation (the amount of heat the material can trap) differs for every product."
• "The heat trapped between layers (such as a blanket and a baby grow) changes the insulation or warmth of the product significantly."
• "Every baby is different, so our room temperature guidance is intended to be used as a guide."

In other words, a chart mapping degrees to togs and garments cannot be correct across products, because the insulation depends on which product. The Lullaby Trust's substitute is to follow the manufacturer's own tog guide for the bag you actually own, which is the only guide that describes the thing in your cot.

What a tog is

Red Nose Australia gives the definition: TOG stands for Thermal Overall Grade and indicates how much a fabric insulates. Higher number, warmer product. Lower togs for warmer rooms, higher for cooler. In Australia, ratings run from 0.2 to 3.5. Red Nose's advice is the same as the UK's: use the guide on the product's packaging.

The layering rules that do generalise

The Lullaby Trust publishes several rules that hold regardless of product:

• One blanket doubled over counts as two blankets. If your baby needs an extra blanket, make it a lightweight one.
• Two 1.0 tog bags do not make 2.0 tog. "Air becomes trapped between layers and increases the warmth. Avoid doubling up on layers this way, as it could increase the risk of SIDS."
• Do not add blankets on top of a sleeping bag. If your baby feels cold, add a clothing layer or use a higher tog bag.
• Weighted bedding is not recommended for babies under one, because of overheating, head covering, and pressure on the chest. The AAP says the same about weighted swaddles and blankets.
• Sleeping bags are fitted by weight, not age, and should be well fitted at the neck and shoulders so a baby cannot wriggle down inside. The British safety standard is BS EN 16781:2018.

What to dress your baby in

The Lullaby Trust's guidance, tied to its own 16 to 20°C range rather than to a tog number: between 16 and 20°C, a baby grow and a well-fitting sleep bag, or a baby grow with a firmly tucked in lightweight blanket. Cooler than 16°C, add a clothing layer or a higher tog bag rather than piling blankets on top. Warmer than 20°C or in hot weather, a lightweight layer such as a short sleeve bodysuit. In really hot weather, "it's fine to have your baby in a short sleeve vest or even just a nappy".

Hot nights

When you cannot get the room down, the Lullaby Trust suggests lighter bedding and fewer layers, opening the bedroom door and a window if it is safe, keeping curtains closed in the daytime, and using a fan but not aimed directly at your baby. Keep the cot away from radiators, direct sunlight and air conditioning. In hot weather, fully breastfed babies need no extra water until they are on solids but may feed more often; formula-fed babies can be offered a little cooled boiled water.

If your baby is unwell

The Lullaby Trust: dress your baby for their environment, and resist the temptation to wrap an unwell baby up more than usual. If your baby has a fever or you are worried, contact your GP or call 111 in the UK.

When to ask

Call your GP or 111 if your baby has a high temperature, is difficult to rouse, is breathing rapidly, or seems significantly unwell. Speak to your health visitor if you cannot keep your home warm enough and are worried about it — that is a common conversation and there is practical help, including grants and baby banks, rather than judgement.