It’s 11pm, you’ve just settled the baby, and now you’re standing over the cot wondering if they’re too hot, too cold, or just right. The sleeping bag says 2.5 TOG. The room thermometer reads 22°C. Is that okay? Should you take a layer off? Add a vest? You’ve googled it three times this week and every website gives slightly different advice.
TOG ratings on baby sleeping bags should make life simpler, but the combination of room temperature, clothing layers, and TOG values creates a matrix that new parents find genuinely confusing. Especially when every degree of temperature seems to require a different combination, and overheating is linked to increased SIDS risk — which is the kind of information that keeps you awake even after the baby falls asleep.
This guide cuts through the confusion with clear, practical advice based on Lullaby Trust guidelines and NHS recommendations. No vague hand-waving — actual room temperatures matched to specific TOG values and clothing combos.
What Is TOG and Why Does It Matter?
TOG stands for Thermal Overall Grade. It’s a measure of thermal resistance — how well a fabric insulates. The higher the TOG, the warmer the item. It’s the same rating system used for duvets, though baby sleeping bag TOGs work on a smaller scale.
Common TOG ratings for baby sleeping bags:
- 0.5 TOG — lightweight, minimal warmth. For hot rooms or summer
- 1.0 TOG — light insulation. For warm rooms
- 1.5 TOG — moderate warmth. A versatile middle-ground option
- 2.5 TOG — standard warmth. The most commonly used rating in the UK
- 3.5 TOG — heavy warmth. For cold rooms in winter (less common)
The reason TOG matters specifically for babies is that they can’t regulate their body temperature as effectively as adults. They can’t kick off a duvet if they’re hot or pull one up if they’re cold. A sleeping bag with a fixed TOG rating gives you more predictable warmth than loose blankets — which is why the Lullaby Trust recommends sleeping bags over blankets and duvets for babies under 12 months.
Overheating is a known risk factor for SIDS (Sudden Infant Death Syndrome). This isn’t meant to scare you — it’s meant to explain why getting the TOG right matters more than just comfort. The NHS advises keeping the baby’s room between 16-20°C, with 18°C considered ideal.
Room Temperature and TOG: The Practical Guide
Here’s what to use at each room temperature. These follow the most widely recommended guidelines from UK baby sleep organisations.
Below 16°C:
- TOG: 2.5 or 3.5
- Clothing underneath: Long-sleeved bodysuit plus sleepsuit (babygro)
- Notes: Rooms this cold are uncommon in UK homes with central heating, but can happen in older houses, draughty bedrooms, or during power cuts in winter. A 3.5 TOG bag with layers is appropriate here.
16-18°C:
- TOG: 2.5
- Clothing underneath: Long-sleeved bodysuit plus sleepsuit
- Notes: This is the cooler end of the recommended range. A 2.5 TOG bag — the UK standard — with a full outfit underneath keeps baby warm without overheating.
18-20°C:
- TOG: 2.5
- Clothing underneath: Long-sleeved bodysuit only (no sleepsuit)
- Notes: This is the sweet spot. Most UK bedrooms sit in this range during autumn and spring. A 2.5 TOG bag with just a bodysuit underneath is usually perfect.
20-22°C:
- TOG: 1.0 or 1.5
- Clothing underneath: Short-sleeved bodysuit
- Notes: Getting warmer. Drop to a lighter TOG bag. If your room sits consistently at 21-22°C (common in modern well-insulated homes), a 1.0-1.5 TOG with a short-sleeved vest is right.
22-24°C:
- TOG: 0.5 or 1.0
- Clothing underneath: Short-sleeved bodysuit or just a nappy
- Notes: This is warm. In summer or in rooms with poor ventilation, drop to the lightest TOG available. If the room is above 23°C with a 0.5 TOG, your baby may only need a nappy underneath.
Above 24°C:
- TOG: 0.5 or none (just a cotton sheet)
- Clothing underneath: Nappy only
- Notes: Too hot for most sleeping bags. During UK heatwaves, consider ditching the sleeping bag entirely and using a single cotton muslin or sheet. Keep curtains closed during the day and open windows at night.
How to Check Your Baby’s Temperature
You can’t rely on how their hands and feet feel — these are often cool even when a baby is perfectly warm. It’s normal and doesn’t mean they’re cold.
The reliable check points are:
- Back of the neck — should feel warm, not hot or sweaty
- Chest or tummy — should feel warm to the touch
- Between the shoulder blades — another reliable warm spot
If the skin feels hot, clammy, or sweaty at these points, your baby is too warm. Remove a layer or switch to a lower TOG.
If the skin feels cool at the chest or tummy (not just hands and feet), add a layer or move to a higher TOG.
A room thermometer is essential. The cheap digital ones (about £5-8 from Amazon UK, Boots, or Argos) are perfectly accurate and many baby monitors have room temperature displays built in. Place it at cot level, not on a high shelf — temperature varies by height in a room.
Seasonal TOG Planning in the UK
The UK climate means most parents need at least two TOG ratings to cover the year. Three is ideal. Here’s a practical buying plan:
Essential (covers most of the year):
- 2.5 TOG — your workhorse bag for October through April. This handles the majority of UK bedroom temperatures (16-20°C).
- 1.0 TOG — for the warmer months (May through September) and well-heated bedrooms.
Nice to have:
- 0.5 TOG — for heatwaves and very warm rooms. UK summers are getting warmer, so this is increasingly useful rather than a luxury.
Optional:
- 3.5 TOG — only needed if your baby’s room regularly drops below 16°C. Most UK homes with central heating won’t need this.
Budget-wise, you’re looking at about £15-30 per sleeping bag depending on brand and size. The Gro Company (Grobag), Tommee Tippee, and MORI are popular UK brands. Supermarket own-brands from Sainsbury’s and Tesco are notably cheaper (about £8-12) and perfectly functional.
Buy two in the same TOG rating so you always have a clean one available when the other is in the wash. Sleeping bag emergencies at 2am are not fun.
TOG and Clothing Combinations: The Quick Reference
For those middle-of-the-night moments when you need a fast answer:
2.5 TOG bag:
- 16-18°C → long-sleeved bodysuit + sleepsuit
- 18-20°C → long-sleeved bodysuit only
- 20-22°C → short-sleeved bodysuit only
1.0 TOG bag:
- 20-22°C → short-sleeved bodysuit
- 22-24°C → short-sleeved bodysuit or nappy only
0.5 TOG bag:
- 24°C+ → nappy only
- 22-24°C → short-sleeved bodysuit
Print this out and stick it on the nursery wall. Seriously. At 3am when you’re half-asleep, a chart on the wall beats trying to remember or googling on your phone with one eye closed.
Common TOG Mistakes
Using a duvet instead of a sleeping bag: For babies under 12 months, duvets are not recommended by the NHS or Lullaby Trust. They can ride up over the baby’s face and the TOG can’t be reliably controlled because babies kick duvets into bunches. Sleeping bags stay put and maintain consistent warmth.
Adding hats indoors: Babies regulate temperature partly through their heads. Putting a hat on a baby indoors can cause overheating. Hats are for outdoors only, unless you’re in a hospital immediately after birth.
Doubling up blankets over a sleeping bag: If the room is cold enough to need extra warmth beyond the sleeping bag, switch to a higher TOG rather than adding blankets on top. Loose blankets are a suffocation risk for babies who can’t yet roll and move freely.
Ignoring room temperature changes overnight: Your bedroom might be 20°C at bedtime but drop to 16°C by 4am as the heating goes off. A 2.5 TOG bag handles this range well, which is partly why it’s the UK default. If your heating is on a timer, consider what temperature the room will be at its coldest, not just at bedtime.
Assuming all sleeping bags are the same: Cheaper sleeping bags sometimes have uneven fill distribution, meaning parts of the bag are warmer than others. Gently shake and feel the bag before use — the fill should be evenly spread throughout. Brands like Grobag and MORI tend to have more consistent construction.
Transitioning Between TOGs
When seasons change, don’t switch TOGs overnight. Transition gradually:
Moving from 2.5 to 1.0 TOG (spring):
- Start by removing a clothing layer while keeping the 2.5 TOG
- After a few days, switch to 1.0 TOG with the same clothing you had with 2.5
- Then remove a layer if needed
Moving from 1.0 to 2.5 TOG (autumn):
- Start by adding a clothing layer with the 1.0 TOG
- After a few days, switch to 2.5 TOG and reduce clothing back to the standard combo
This gradual approach lets you monitor how your baby responds. Check their neck and chest temperature each morning during the transition.
If you’re using a bedside crib where the baby is close to you, remember that your body heat warms the immediate area slightly — particularly in co-sleeping setups with the crib side down. Factor this into your TOG choice by erring slightly cooler.
When to Stop Using TOG-Rated Sleeping Bags
Most children transition out of sleeping bags between 18 months and 3 years. There’s no fixed age — it depends on the child.
Signs they’re ready to move on:
- Climbing out of the sleeping bag regularly
- Consistently pulling it off during the night
- Moving to a toddler bed where they need more freedom of movement
- Asking for a “big kid” duvet (toddlers can be surprisingly specific about bedding preferences)
When you do transition, a low-TOG duvet (4.0-7.0 TOG for a toddler duvet) with a fitted sheet is the standard next step. Keep the room temperature the same and check on them the first few nights to make sure they’re comfortable. Some toddler night lights can double as room thermometers, which helps during the transition.
Frequently Asked Questions
What TOG sleeping bag should I use for a newborn in the UK? For most UK bedrooms (16-20°C), a 2.5 TOG sleeping bag is the standard choice for newborns. Make sure it’s sized for newborns (usually 0-6 months) with a snug neck opening that your baby can’t slip down into. Dress them in a long-sleeved bodysuit underneath for rooms at 18-20°C, or add a sleepsuit for rooms below 18°C.
Is 2.5 TOG too warm for summer? Usually yes. UK summer bedrooms often reach 20-24°C, and a 2.5 TOG bag at those temperatures risks overheating. Switch to a 1.0 TOG (for 20-22°C rooms) or a 0.5 TOG (above 22°C). During heatwaves above 25°C, consider just a muslin or cotton sheet instead of a sleeping bag.
How do I know if my baby is too hot in their sleeping bag? Feel the back of their neck or their chest. If the skin is hot, clammy, or damp with sweat, they’re too warm. Remove a layer of clothing or switch to a lower TOG bag. Don’t rely on hands and feet — these are naturally cooler in babies and aren’t reliable indicators of core temperature.
Can I use a blanket instead of a TOG-rated sleeping bag? The Lullaby Trust and NHS recommend sleeping bags over loose blankets for babies under 12 months. Sleeping bags can’t be kicked over the face, maintain consistent warmth, and have standardised TOG ratings. If you do use blankets, they should be cellular (with holes) and tucked firmly under the mattress with the baby’s feet at the foot of the cot.
Do I need different TOG sleeping bags for different seasons? In the UK, yes. At minimum you need two: a 2.5 TOG for the cooler months (roughly October-April) and a 1.0 TOG for warmer months (May-September). Adding a 0.5 TOG for heatwaves is increasingly worthwhile as UK summers get warmer. Buy two of each TOG rating so you always have a clean one ready.