TOG stands for Thermal Overall Grade, and it tells you how much warmth a baby sleep sack or blanket traps. The higher the TOG number, the warmer the product. Matching the right TOG to your nursery temperature, then choosing the right clothing layers underneath, keeps your baby comfortable and safe through the night.
What TOG Ratings Mean
A TOG rating measures a fabric’s thermal resistance, or its ability to insulate and hold heat. Sleep sacks, swaddles, and baby blankets are rated on a scale that typically runs from 0.2 (barely any insulation) up to 3.5 (heavy winter warmth). The number is printed on the product label or packaging, and it’s the single most useful piece of information for deciding how to dress your baby for sleep.
The key variable is your nursery temperature. A room thermometer is worth the small investment, because guessing often leads to overdressing. Here are the standard recommendations:
- Above 80°F (27°C): 0.2 TOG
- 73–79°F (23–26°C): 0.5 TOG
- 68–73°F (21–23°C): 1.0 TOG
- 61–68°F (16–20°C): 2.5 TOG
- Below 60°F (under 16°C): 3.5 TOG
Most homes sit somewhere between 61°F and 73°F at night, which means a 1.0 or 2.5 TOG sleep sack covers the majority of the year for most families.
The Ideal Nursery Temperature
The Lullaby Trust, a UK safe-sleep organization widely cited by pediatric groups, recommends keeping the nursery between 16°C and 20°C (roughly 61°F to 68°F). That range, combined with a lightweight, well-fitting sleep bag, is considered both comfortable and safe. Many parents keep rooms warmer than this, especially in summer or in homes without air conditioning, and that’s fine as long as you adjust the TOG and clothing layers down accordingly.
What to Wear Under the Sleep Sack
The clothing underneath matters just as much as the TOG rating itself. Air gets trapped between layers and adds warmth beyond what the TOG number alone would suggest. Doubling up on sleep sacks (wearing two 1.0 TOG bags, for example) does not simply add up to 2.0 TOG. It can trap significantly more heat than expected and increase the risk of overheating, which is linked to SIDS.
Because every product uses different materials and blends, no single chart works perfectly across all brands. The Lullaby Trust specifically notes that they can’t provide one universal layering guide for this reason. Your best bet is to follow the manufacturer’s own tog guide printed on or included with the sleep sack, then use these general principles:
- Room warmer than 75°F (24°C): A diaper alone, or a short-sleeve bodysuit with a 0.2–0.5 TOG sack.
- Room around 68–73°F (20–23°C): A short-sleeve bodysuit under a 1.0 TOG sack.
- Room around 61–68°F (16–20°C): A long-sleeve sleepsuit (sometimes called a baby grow) under a 2.5 TOG sack.
- Room below 61°F (16°C): A long-sleeve sleepsuit under a 3.5 TOG sack. Add an extra layer of clothing rather than an extra blanket on top.
In very hot weather, it’s perfectly fine for your baby to sleep in just a diaper with no sleep sack at all.
Why Fabric Choice Matters
Two sleep sacks with the same TOG rating can feel quite different depending on the material. Cotton and bamboo are the two most common options, and each behaves differently against your baby’s skin.
Organic cotton tends to feel sturdier and provides more stable temperature regulation. It’s breathable without running particularly cool or warm. Bamboo fabric is noticeably softer, but parent experiences are mixed: some find it more breathable and great for warm sleepers, while others report that bamboo sleepwear runs surprisingly cold, especially lightweight bamboo sleep-and-plays. If your baby seems to run hot, bamboo may work well. If your baby tends toward the cooler side, cotton is generally the safer bet for consistent warmth at a given TOG.
Whichever fabric you choose, the TOG rating is still the primary guide. The fabric just fine-tunes the experience.
No Hats or Head Coverings Indoors
Babies release a significant amount of body heat through their heads. The American Academy of Pediatrics recommends against covering an infant’s face or head during sleep to prevent overheating and reduce the risk of SIDS. Skip the hat for indoor sleep, even in cooler rooms. If the room is cold enough that you’re tempted to add a hat, it’s better to increase the TOG of the sleep sack or add a clothing layer underneath instead.
How to Handle Seasonal Shifts
Spring and fall are the trickiest seasons because nursery temperatures can swing 10°F or more between afternoon and the middle of the night. The simplest approach is to own two TOG ratings and swap based on what the thermometer reads at bedtime. A 1.0 TOG and a 2.5 TOG cover most situations year-round in temperate climates.
On nights when the temperature is borderline between two TOG ranges, adjust the clothing layer rather than the sack. A 2.5 TOG with a short-sleeve bodysuit runs cooler than a 2.5 TOG with a long-sleeve sleepsuit. This gives you flexibility without buying a third sleep sack. Resist the urge to layer a blanket over a sleep sack. The trapped air between layers creates unpredictable insulation and increases overheating risk.
Signs Your Baby Is Too Warm
The best spot to check your baby’s temperature is the chest or back of the neck, not the hands or feet (which are often cool even when a baby is perfectly warm). If the skin there feels hot or damp, your baby is likely overdressed. Other signs to watch for:
- Sweating: Especially around the neck, back, and underarms.
- Heat rash: Small red bumps, often on the neck or chest.
- Rapid breathing or unusual fussiness: An overheated baby may breathe faster than normal or become irritable.
- Unusual lethargy: Some babies become very quiet and still when too warm, which can look like deep sleep but is worth checking on.
If your baby’s body temperature rises above 100.4°F (38°C), remove a layer and check again in 15 to 20 minutes. A normal range for infants is between 97.7°F and 100.4°F (36.5°C to 38°C).
Putting It All Together
The routine is straightforward once you get the hang of it: check the room temperature, pick the matching TOG, dress your baby in one appropriate layer underneath, and skip anything on the head. Do a chest check about 10 minutes after putting your baby down to confirm they feel warm but not hot or sweaty. Over a few nights, you’ll develop a feel for which combination works best for your baby, your home, and the season.