TOG rating and room temperature guide

What should my baby wear to sleep?

It is one of the most searched questions in the first year, and the internet answers it with enormous confidence: charts, grids, colour-coded tables matching a room temperature to a TOG value and an exact outfit. The confidence is misplaced. The organisation most people are ultimately trying to quote — the Lullaby Trust, whose safer-sleep guidance underpins what UK midwives and health visitors say — explicitly declines to publish that chart, and has explained why.

Start with the room, not the outfit

The published figure is a room temperature of 16 to 20°C. Cooler than most people keep a house, which surprises new parents, and deliberately so: overheating is a risk factor for sudden infant death, and the guidance is set to keep babies from getting too hot rather than to make a room feel pleasant to an adult standing in it fully dressed.

A room thermometer is a cheap and useful thing, and sleeping in the same room as your baby for the first six months, day and night, is strongly recommended in its own right. But treat the number as a starting point. A 16°C room and a 20°C room both sit inside the recommendation, and they are not the same room to sleep in.

Why there is no honest chart

The reasons the Lullaby Trust gives are practical, not evasive. Two sleeping bags both labelled 2.5 TOG can be made of different fibres in different proportions and trap heat differently. The moment you add a layer, the insulation of the combination is not the sum of the parts, because air trapped between layers does its own work. And babies differ. A chart that flattens all of that into one cell per temperature is making up the missing precision.

This matters because the charts circulating online are mostly produced by companies selling sleeping bags. That does not make them dishonest, but it does make them guidance for one product line, presented as if it were universal. If you own a sleeping bag, the manufacturer's guidance for that bag is the right thing to follow. What you should not do is apply one brand's grid to another brand's product, or to blankets.

Check the baby, not your own hands

The single most useful technique costs nothing. Feel your baby's chest or the back of their neck. If the skin there is hot or sweaty, they have too many layers and you should remove one or more. Hands and feet run cooler than the core in babies, and this is normal — but it is also the most common reason parents add a layer that was not needed. Cold hands are not evidence of a cold baby.

The rules that do not move with the thermometer

Two things hold at every temperature. Babies do not need hats indoors: they lose heat through the head, and that is how they regulate their temperature, so an indoor hat removes the mechanism. And babies should not sleep under a duvet or a quilt. Light bedding, firmly tucked, or a well-fitting baby sleep bag, is the shape of the advice. A clear cot — no pillows, bumpers, pods or loose bedding — is part of the same picture.

When the room will not cooperate

In a heatwave, keeping a bedroom at 20°C is often impossible, and the guidance accepts that rather than pretending otherwise. The advice becomes lighter bedding and lighter clothing, opening the bedroom door and a window where it is safe to do so, and a fan to cool the room without aiming it directly at the baby. Fluids matter too: a fully breastfed baby needs no extra water before solids but may want to feed more often in hot weather, while a formula-fed baby can be offered a little cooled boiled water alongside usual feeds.

In winter the reverse problem appears, and the answer is reassuringly boring. It is rarely necessary to run heating all night. An extra layer will usually cover the gap if the room runs below the recommended range. Keep the cot away from radiators, heaters and direct sun, and keep the hat off indoors.

Sleeping bags, swaddling and fit

A baby sleep bag removes a whole category of worry, because it cannot be kicked off and cannot ride up over the face. The number on the label is less important than the fit: it should be snug around the neck and arm holes, so the baby cannot slip down inside it, and sized for the baby rather than bought large to last. Whatever you use, the same principle applies as with bedding — if in doubt, fewer layers and a cooler room is the direction the guidance points.

What to take from this

You are not missing a secret chart. There genuinely is not one, and the absence is a considered position by the people best placed to publish it, not an oversight. What you have instead is a target range of 16 to 20°C, a clear cot, no hat indoors, no duvet or quilt, and a hand on the chest or the back of the neck to check. That is less satisfying than a grid, and it is what the evidence actually supports.

If your baby seems unwell, or is unusually hot, floppy or hard to rouse, this is not a dressing question. Contact your GP, call 111, or in an emergency call 999.