What tog sleeping bag for a newborn?

Last updated: 7 July 2026 · A guide, not medical advice

The short answer

For most UK nurseries sitting at 16-20°C, a 2.5 tog sleeping bag with a short-sleeved bodysuit and a sleepsuit is the standard choice for a newborn. In a warmer room (24°C+) drop to a 1.0 or 0.5 tog; in a cold room under 16°C use a 3.5 tog or add a layer. Always go by a room thermometer, not by how the room feels to you.

What tog does a newborn need, by room temperature?

Tog measures how warm the bag is. The right one depends almost entirely on your room temperature at night:

• Over 24°C, 0.5 tog, or just a short-sleeved bodysuit in a light bag.
• 20-24°C, 1.0 tog.
• 16-20°C, 2.5 tog. This is the everyday all-rounder most families own.
• Under 16°C, 3.5 tog, or a 2.5 tog with an extra layer underneath.

A newborn can't regulate their own temperature the way an older child can, so getting the room right matters more in these first months than at any other age. A cheap room thermometer is one of the most useful things you can buy.

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Getting the size right (this matters for safety)

With newborns, size is as important as tog. A bag that's too big lets baby wriggle down inside it, which is a suffocation risk. So buy for your baby's current weight, never to "grow into".

Most newborn bags have a minimum weight of around 4 kg (8.8 lb). If your baby is smaller than that (and plenty of newborns are), look for a bag specifically rated from birth, or one with poppers that shorten it. Check the label's weight range before every new size.

What to dress a newborn in inside the bag

The bag sets the base warmth; clothing does the fine-tuning. In a typical 2.5 tog bag at 16-20°C, a short-sleeved bodysuit plus a sleepsuit is standard. As a rough guide:

• Warm room: short-sleeved bodysuit only.
• Average room: bodysuit + sleepsuit.
• Cold room: bodysuit + sleepsuit, and move up to a 3.5 tog bag.

Adjust the clothing before you adjust the bag, it's simpler, and safer than swapping to a heavier tog you might not need.

How to tell if your newborn is too hot or too cold

Don't judge by their hands or feet, those are naturally cooler and aren't a reliable guide. Instead, feel the chest, tummy or back of the neck. It should feel comfortably warm, not sweaty or clammy. Signs a baby is too hot include damp hair, flushed cheeks, a hot back and rapid breathing. If in doubt, remove a layer. Overheating is riskier than being a touch cool.

Safe-sleep basics that go with the bag

A sleeping bag is only part of safe sleep. Alongside the right tog and size:

• Always place baby on their back to sleep.
• Never add a loose blanket, quilt or pillow on top of the bag.
• No hats indoors, babies lose heat through the head and can't cool down with one on.
• Keep the cot clear of bumpers and soft toys.
• Use a room thermometer and keep the nursery around 16-20°C.

This guide is general information, not medical advice. For trusted, up-to-date safe-sleep guidance, see The Lullaby Trust, and speak to your health visitor if you have any concerns about your baby.

Work out the exact tog for your room

Not sure what your nursery runs at, or what to pair with the bag you already have? Our baby sleeping bag tog tool gives you the right tog and the clothing to match in seconds, just enter your room temperature.