Baby Sleeping Bag TOG Guide: Choosing the Right Warmth

Table of Contents

• Why TOG Ratings Matter for Safe Baby Sleep
• Baby Sleeping Bag TOG Chart: Matching Warmth to Room Temperature
  • The 16-20°C Range: Most Nurseries Sit Here
  • Warmer and Cooler Rooms: When to Adjust
• What to Wear Under a Baby Sleeping Bag
  • Layering with Aurora Baby Co. Jumpsuits
• How to Check if Baby Is Too Hot at Night
• Baby Sleeping Bag Sizes and Age Guide
• Common TOG Mistakes Parents Make
• Conclusion: Choosing the Right TOG for Your Baby
• Frequently Asked Questions

Last Updated: October 5, 2026

Why TOG Ratings Matter for Safe Baby Sleep

A baby sleeping bag TOG guide starts with one number that decides whether your baby sleeps safely or overheats: the TOG rating. TOG stands for Thermal Overall Grade, a standardised measure of how much warmth a sleeping bag traps. The higher the number, the warmer the bag. Get it wrong and you either cook your baby or leave them cold enough to wake every hour.

A bag rated 2.5 TOG looks almost identical to one rated 1.0 TOG on the shelf, yet the difference in warmth is significant.

Overheating is one of the few modifiable risk factors linked to sudden infant death syndrome, and the Lullaby Trust's safer sleep guidance is clear that room temperature and bedding choice both matter. That is why the TOG system exists: it gives you a predictable way to match bedding to the temperature of the room, rather than guessing by feel.

Below, we break down exactly which TOG rating suits which room temperature, what to layer underneath, and the mistakes we see parents make most often.

Baby Sleeping Bag TOG Chart: Matching Warmth to Room Temperature

The right TOG rating is determined by your nursery's temperature, not by the season on the calendar. A well-insulated modern flat can sit at 22°C in January, while an old cottage bedroom might drop to 15°C in June. Measure the room, then choose the bag.

Here is the reference chart we recommend printing and sticking inside the nursery cupboard door:

The 16-20°C Range: Most Nurseries Sit Here

Most parents find their nursery settles somewhere between 16°C and 20°C overnight, and this is the range where a 1.5 TOG to 2.5 TOG bag does the job. A 2.5 TOG bag is the workhorse of this bracket: warm enough for a room hovering around 17°C, but not so heavy that a 20°C night becomes uncomfortable.

If your thermometer reads 18-20°C, a 1.5 TOG bag paired with a long-sleeve bodysuit is usually plenty. At 16-17°C, step up to 2.5 TOG. The difference of one degree at the cooler end matters more than parents expect.

Warmer and Cooler Rooms: When to Adjust

Rooms above 23°C call for a 0.5 TOG or 1.0 TOG bag, and possibly just a short-sleeve bodysuit underneath. Rooms below 16°C need a 3.5 TOG bag, and you should also check for draughts before simply adding layers. A cold room is often a ventilation problem, not a bedding problem.

The common mistake here is sizing up the TOG instead of fixing the room. A 3.5 TOG bag in a draughty room still leaves a baby's head and face exposed to cold air, and the bag itself becomes a hazard if the room then warms up overnight.

What to Wear Under a Baby Sleeping Bag

What you layer under the bag matters as much as the bag itself. The sleeping bag replaces a blanket, not the clothing underneath it, so you still need a base layer appropriate to the room.

Our rule of thumb: one more layer than you would wear to sleep in the same room.

• 24°C+: Short-sleeve bodysuit only, or a nappy and a 0.5 TOG bag
• 21-23°C: Short-sleeve bodysuit under a 1.0 TOG bag
• 18-20°C: Long-sleeve bodysuit under a 1.5 TOG bag
• 16-17°C: Long-sleeve bodysuit plus a 2.5 TOG bag
• Below 16°C: Long-sleeve bodysuit and a 3.5 TOG bag, plus a vest if the room is genuinely cold

Never add a hat indoors. Babies lose heat through their heads, and a hat in a heated room is one of the fastest routes to overheating.

Layering with Aurora Baby Co. Jumpsuits

For the base layer, we recommend a soft, breathable jumpsuit rather than a bulky sleepsuit. Our Long-Sleeve Baby Jumpsuit in a cotton blend is cut for easy layering under a sleeping bag, with popper fastening for quick night-time changes and a fabric that washes well at 30°C.

For warmer rooms, our Bamboo Fibre Baby Jumpsuit is the better choice. Bamboo fibre is soft and breathable, which suits sensitive skin and keeps a baby from getting clammy under a lighter TOG bag. On genuinely cold nights, the Hooded Knitted Jumpsuit works as a cosy outer layer for daytime, though we would not recommend the hood for overnight sleep.

How to Check if Baby Is Too Hot at Night

Checking whether your baby is too hot takes ten seconds and should be done at every night feed. Slide your hand flat against the back of their neck or their chest. That area tells you the truth; hands and feet are almost always cooler than the core and are not a reliable guide.

If the back of the neck is hot, damp, or clammy, your baby is too warm. Remove a layer or drop to a lower TOG bag. If the skin is cool to the touch, add a layer. Comfortably warm and dry is the target.

Hooded Knitted Jumpsuit for Baby, Cosy All-in-One Romper →

Other signs of overheating to watch for:

• Flushed or red cheeks
• Rapid breathing or restlessness
• Sweat behind the knees or in the neck folds
• A heat rash appearing across the chest or back

If you notice any of these, act before the next sleep cycle. According to NHS guidance on keeping your baby safe in hot weather, babies can overheat quickly, and a cooler room with fewer layers is always the safer direction to err.

Baby Sleeping Bag Sizes and Age Guide

Baby sleeping bag sizes follow your baby's weight and height, not their age alone. A bag that is too large lets a baby slip down inside it, which is a suffocation risk. A bag that is too small restricts movement and rides up around the neck.

Two fit checks matter more than the label. First, the neck opening should not be loose enough for your baby's head to pass through. Second, your baby's feet should not be able to reach the bottom of the bag and bunch it up. If either happens, size down.

Never use a sleeping bag on a baby under 4 kg or under 8-9 weeks old, and never use one in a car seat or pushchair where the harness needs to sit flat against the body.

Common TOG Mistakes Parents Make

The same handful of errors come up again and again. Avoiding them is simpler than most parents expect.

1. Choosing by season instead of temperature. A mild January day in a warm flat needs a lower TOG than a cold June night in a stone cottage. Buy a thermometer before you buy a bag.
2. Adding blankets on top of the bag. A sleeping bag is designed to be the only bedding. Adding a blanket over it defeats the purpose and creates a loose covering near the face.
3. Skipping the base layer calculation. Parents often pick the right TOG bag and then dress the baby in a thick sleepsuit underneath, which is effectively two extra layers.
4. Keeping the same bag all year. Most families need at least two TOG ratings: a 1.0 or 1.5 for summer and a 2.5 for winter.
5. Ignoring the neck fit as baby grows. A bag that fitted at three months can become a slip risk by six. Check the neck opening every few weeks.

If you are unsure between two TOG ratings, choose the lower one and add a base layer. It is far easier to warm a baby up than to cool one down once they are overheated.

Conclusion: Choosing the Right TOG for Your Baby

Getting the TOG right comes down to three habits: measure the room, match the bag to the temperature, and check the back of your baby's neck at every feed. Do those three things and you will rarely get it wrong, whatever the season throws at you.

At Aurora Baby Co., we designed our sleep-friendly jumpsuits to sit comfortably under any TOG bag, in fabrics soft enough for newborn skin and breathable enough for warmer rooms. Explore our baby clothing range and start shopping for base layers that make night-time layering simple.