The TOG rating guide for sleep sacks
Exactly what TOG means, how to match the right TOG to your room, and why most brand charts are slightly off.
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TL;DR
TOG (Thermal Overall Grade) measures how much warmth a sleep sack provides. The four common ratings are 0.5, 1.0, 1.5, and 2.5. Match the TOG to your nursery temperature: 0.5 for rooms above 74°F, 1.0 for 70-74°F, 1.5 for 65-70°F, 2.5 for under 65°F. Most US homes year-round work with a 1.0 TOG and seasonal adjustments to the inner layer rather than rotating sleep sacks.
Temperature and sleep sack choice work together with everything else - the schedule, the falling-asleep plan, the room setup. Get your wake windows dialed in too while you're optimizing.
What TOG actually is
TOG is a textile insulation measurement that originated in the UK clothing and bedding industry. It quantifies thermal resistance - how well a fabric blocks heat loss.
The math: 1 TOG equals 0.1 m² K/W (metric thermal resistance units). The higher the TOG, the more insulating the fabric.
For sleep sacks, four ratings cover almost everything you'd need:
- 0.5 TOG. Light, summer-weight. Single layer of muslin or thin cotton.
- 1.0 TOG. Standard mid-weight. Quilted cotton or bamboo.
- 1.5 TOG. Mild cool-weather. Slightly thicker quilting.
- 2.5 TOG. Cold weather. Heavily quilted or fleece-lined.
A few brands also make 3.5 TOG for extreme cold, but most homes never need this.
The temperature-to-TOG chart
This is the chart sleep sack brands and pediatric sleep consultants agree on, with light cleaning for clarity.
Room is over 76°F (hot). No sleep sack. Onesie or diaper alone. A 0.2 TOG muslin sleep sack if you must have something.
Room is 72-76°F (warm). 0.5 TOG with short-sleeve onesie underneath.
Room is 68-72°F (recommended). 1.0 TOG with long-sleeve onesie or short-sleeve pajamas underneath.
Room is 65-68°F (cool). 1.5 TOG with long-sleeve pajamas underneath.
Room is under 65°F (cold). 2.5 TOG with footed long-sleeve pajamas underneath.
Why brand charts vary
If you look at five different sleep sack brands, you'll see five slightly different recommendations for the same room temperature. Here's why.
Fabric variations. A 1.0 TOG bamboo is warmer-feeling than a 1.0 TOG polyester even at the same rating. Bamboo holds moisture differently.
Cut variations. A fitted sleep sack with snug arm holes feels warmer than a roomy one. Same TOG, different real-world warmth.
Sleeve variations. Sleeveless vs short-sleeve vs long-sleeve at the same TOG rating provides different warmth.
The bottom line: TOG is a guideline, not a guarantee. Watch your baby's chest temperature (the real check) and adjust.
The chest-and-back temperature check
Forget the hands and feet - those are always cool on babies. The actual check:
Put your palm on baby's chest or back of neck.
- Warm and dry: Perfect.
- Cool: Add a layer or upgrade TOG.
- Sweaty or hot: Remove a layer or downgrade TOG.
Do this check 1-2 hours after baby falls asleep when their body temperature has stabilized. Checking at the moment you put them down can be misleading.
How many TOGs you actually need
Most US families need two: a 1.0 TOG and a 2.5 TOG.
The 1.0 covers spring, summer, and fall in most homes with AC. The 2.5 covers winter in colder regions or homes that don't heat well at night.
Add a 0.5 TOG if:
- You live somewhere hot (Phoenix, Miami, Houston) and your AC struggles.
- Your home stays consistently above 75°F at night.
- You have a particularly hot sleeper baby.
Skip the 1.5 TOG unless you really need fine-tuning. Most parents use 1.0 with an extra inner layer instead of a separate 1.5.
Optimize the full sleep environment
TOG is one piece. Schedule, sound, light, and falling-asleep skill matter too. Start with our free wake windows calculator.
Try the calculatorWhat underlayer pairs with each TOG
Sleep sacks should never be the only thing - they're an outer layer over an underlayer. Here's what to pair.
0.5 TOG: Sleeveless onesie or short-sleeve onesie. Diaper alone in very hot weather.
1.0 TOG: Long-sleeve onesie OR short-sleeve pajamas. Most versatile.
1.5 TOG: Long-sleeve onesie plus light pajama bottoms, OR footed cotton pajamas.
2.5 TOG: Footed long-sleeve pajamas, possibly with a thin long-sleeve onesie underneath in the coldest weather.
Don't stack high-TOG sleep sacks with thick fleece pajamas - that's overheating territory. The sleep sack does the insulation; the underlayer is a base.
When to swap TOG vs swap underlayer
The general rule: adjust the underlayer for small temperature changes, swap the TOG for big seasonal changes.
If the room dropped 3 degrees overnight, add a long-sleeve onesie under the 1.0 TOG. Don't rush to swap to 1.5.
If your AC just kicked off because it's October and the room jumped from 68 to 74, then yes - swap from 1.5 to 1.0 TOG.
Two TOGs (1.0 and 2.5) plus 4-5 onesies/pajamas in different sleeve lengths covers the entire year for most families.
Common mistakes
Using the same TOG year-round. A 2.5 TOG in summer = overheating. A 0.5 TOG in winter = cold baby. Adjust seasonally.
Layering blankets over a TOG. Sleep sacks replace blankets. Don't stack.
Trusting the marketing TOG. Some Amazon brands list "comparable to 2.5 TOG" without actual testing. Real TOGs are tested to a textile standard. Look for the actual TOG number in product specs.
Sizing up to be safe. Bigger sleep sacks are warmer (more fabric) but also less safe (slipping risk). Size right, not big.
Forgetting about the head. Babies regulate temperature through their heads. No hats indoors. The TOG of the sleep sack assumes uncovered head.
TOG and SIDS risk
Overheating is associated with increased SIDS risk in babies under 6 months. The AAP recommends keeping the room at a comfortable temperature for a lightly clothed adult (which approximates 68-72°F) and not overdressing baby.
If you're uncertain whether to add a layer or skip one, skip. Baby is safer slightly cool than slightly hot.
Special cases
Premature babies. Often need an additional layer because they have less body fat for insulation. Talk to your pediatrician about specific recommendations - the standard chart may not apply.
NICU graduates. Follow whatever guidance you got from discharge. Sometimes the chart needs to be adjusted up by 0.5 TOG for the first month home.
Sick babies. Don't add layers because they're sick. If they have a fever, you may need to dress lighter, not heavier. Follow your pediatrician's specific guidance during illness.
When to call your pediatrician
- Baby is consistently sweaty even with the lowest TOG.
- Baby's chest is consistently cool even with high-TOG and added layers.
- Suspected fever - take a temperature.
- Unexplained sweating or chills that aren't temperature-related.