It's 9pm, you're standing over the cot, and you genuinely cannot tell whether the singlet is enough or whether you've just put your baby to bed too warm. Then you lie awake wondering. Almost every new parent we talk to has had this exact night.
Here's the thing worth knowing up front: it isn't a guessing game, and it doesn't need a spreadsheet either. Once you understand what the TOG number on the label actually means, dressing your baby for bed becomes a two-second decision rather than a nightly worry.
First, a note on where to get advice
We make sleep sacks. We're not midwives, and this guide isn't a substitute for one.
If you want a real person to talk any of this through with, Monique Maitland at The Middee Society is a practising clinical midwife specialist running childbirth education and baby and infant first aid classes across Melbourne, Geelong, Sydney and Brisbane. If you're the sort of parent who feels better for having done the first aid class before you need it, that's the one. Your maternal child health nurse is the other person to lean on, and Red Nose runs a Safe Sleep Advice Line on 1300 998 698 from 9am to 5pm weekdays.
What TOG actually measures
TOG stands for Thermal Overall Grade. It's a measure of how much warmth a garment holds in. Higher number, warmer bag.
One honest caveat that most guides skip: there's no Australian safety standard governing TOG ratings on infant sleeping bags. Red Nose Australia points this out directly, and their advice is to match the TOG to the room and check the manufacturer's own guide rather than assume every brand's 2.5 behaves identically. So treat the ranges below as a starting point, then check the chart that came with your bag.
As a rough guide:
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0.2 to 0.5 TOG. Unpadded and very light, for hot summer rooms.
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1.0 TOG. Light and breathable, for mild rooms.
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2.5 TOG. Padded, for cool nights through autumn and winter.
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3.5 TOG. Heavily padded, for genuinely cold rooms.
The room temperature question, answered honestly
Most articles will tell you to buy a nursery thermometer. Red Nose actually says the opposite: they don't recommend a specific room temperature because there's no evidence a particular number prevents sudden infant death, and they don't consider a room monitor necessary.
Their guidance is simpler. Dress your baby for the temperature of the room the way you'd dress yourself. Comfortably warm, not hot, not cold. Head and face uncovered, always, and no hats indoors.
So why do we still talk in degrees below? Because if you happen to know roughly how warm the room is, matching a TOG to it is faster and less fraught than guessing. Plenty of baby monitors already show room temperature. If yours doesn't, you're not doing anything wrong.
What to put underneath, by room temperature
Cool rooms, roughly 16°C to 20°C
Winter, and those unheated-bedroom nights.
Reach for a 2.5 TOG bag with a long-sleeve cotton suit or ribbed pyjamas underneath. If the room is sitting closer to 16°C, add a long-sleeve cotton singlet under the suit.
Mild rooms, roughly 20°C to 22°C
Spring and autumn, when the weather can't make up its mind.
A 1.0 TOG bag works well with a long-sleeve cotton suit. If you're using a 2.5 TOG bag in this range, a short or long-sleeve bodysuit on its own is usually plenty.
Warm rooms, roughly 22°C to 24°C
A 1.0 TOG bag with a short-sleeve cotton bodysuit, or a light sleeveless singlet.
Hot rooms, 24°C and above
Peak Australian summer.
A 0.2 to 0.5 TOG bag with a short-sleeve singlet, or just a nappy inside a lightweight bag. Less really is fine here. Red Nose also notes that a fan set to oscillate can help on hot nights, as long as it isn't pointed directly at your baby.
Why the fabric matters as much as the layer count
Two layers of cotton and two layers of polyester fleece are not the same thing on a warm night.
Synthetics hold heat and moisture against the skin, which makes it harder for a baby to shed excess warmth. Natural fibres behave better:
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They let air move, so your baby isn't sealed in.
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They pull moisture off the skin, so nobody ends up damp and then chilled.
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They tend to be kinder to newborn skin that's still settling in.
Where the Sleepybelly sacks fit
Our Infant Sleep Sack (3 to 12 months) is made from GOTS-certified organic cotton with a little natural stretch. The part parents tell us they didn't expect to care about is the press-stud removable sleeves, because Australian weather doesn't hold still. Sleeves on when the night turns cool, off when it doesn't, without buying a second bag. The lower bag is cut wide so legs can bend and kick, and the zip opens from the bottom so a nappy change doesn't have to become a full wake-up. We developed it with Carlene Rotblat, a certified sleep consultant, to keep the design practical rather than clever. Check the TOG guide on the product page for the room ranges we've tested it against.
For 0 to 3 months, the Newborn Swaddle Sack gives the same organic cotton with gentle arms-up support.
One safety point we'd rather say too often than not at all: Red Nose advises that wrapping or swaddling must stop once your baby shows any sign of rolling, which is often around three months. That's the moment to move to an arms-free sleep sack. If you want the longer version of that decision, we've written about swaddle sacks versus traditional wraps separately.
How to check whether you got it right
Skip the hands and feet. Cool little hands are normal, and Red Nose says so plainly, so don't let them send you into a spiral at 2am.
Red Nose recommends feeling your baby's tummy, and Raising Children Network covers the same ground as part of a broader safe sleep setup. Some parents find the back of the neck easier to reach without waking anyone. Either works. You're feeling for comfortably warm and dry.
Signs there's a layer too many: the tummy, chest or back of the neck feels hot or clammy, flushed cheeks, faster breathing, unusual restlessness. Take a layer off, or drop to a lower TOG.
Signs there's a layer missing: the tummy feels cool, or your baby keeps waking through the coldest part of the night, often around 4am. Add a long-sleeve cotton layer underneath, or move up a TOG.
If your baby ever shows signs of heat stress, flushed and clammy, Red Nose advises removing bedding or clothing and offering fluids, breast milk under 12 months.
And your own nights
You'll be up in the dark with them, which nobody puts in the guide.
The two things Sleepybelly mums tell us make those hours easier: our Magnesium Body Cream massaged into your neck and shoulders, because feeding and carrying a baby loads up exactly those muscles, and our 3-Piece Maternity Pyjamas, which are cut for feeding access at 3am rather than for a photo shoot.
The short version
Match the TOG to the room, keep the layers underneath cotton, leave the head and face uncovered, and feel the tummy rather than the hands. That's the whole method. Everything else is detail.
Frequently Asked Questions
Should my baby wear socks or mittens inside a sleep sack?
Generally no. The bag already encloses their feet, so extra socks can tip them towards too warm. Mittens are best avoided during sleep too, since babies use their hands to self-soothe and to shed heat.
What should my baby wear under a 2.5 TOG sleep sack in winter?
In a cool room, a long-sleeve cotton suit or ribbed pyjama set. If the room is closer to 16°C, add a light cotton singlet underneath. Check your bag's own TOG chart, because ranges vary between brands.
Is it okay if my baby's hands feel cold inside their sleep sack?
Yes. Red Nose states this outright: cool hands and feet are normal and not a reason to worry. Feel the tummy instead. If that's warm and dry, you're fine.
Do I need a room thermometer?
No. Red Nose doesn't consider one necessary. It just makes matching a TOG a little quicker if you already have one built into your monitor.
The information in this article is general in nature and intended as comfort support only. It is not medical advice. Always consult your midwife, GP, or a qualified healthcare provider for guidance specific to your situation.
