From TOG Value to Age-Appropriate Size: How to Choose a Baby Sleep Sack
How Should I Look at TOG Value and Size When Choosing a Sleep Sack?
What Exactly Is TOG?
TOG is a thermal index that quantifies how well a fabric traps heat, and it has been a standard in the European baby product market for a long time. While not all products in Korea are labeled with TOG yet, knowing the recommended TOG for different room temperatures can help you avoid the mistake of guessing thickness every time the season changes. Even with the same TOG value, the comfort your baby feels can vary depending on the lining material's moisture-wicking ability and softness, so you should pay as much attention to whether the lining absorbs sweat well and feels soft as you do to thickness.
TOG Standards by Room Temperature and Season
| Room Temperature | Season | Recommended TOG |
|---|---|---|
| 24–27°C | Summer | 0.5 TOG |
| 20–23°C | Spring and Fall | 1.0–2.0 TOG |
| 16–19°C | Early Winter | 2.5 TOG |
| 16°C or Below | Deep Winter | 3.5 TOG |
If your room temperature falls on the borderline, it's better to adjust with the thickness of the pajamas you dress your baby in underneath. Layering a thin sleep sack with an additional garment inside responds more flexibly to your baby's body temperature changes than using one thick sleep sack.
How to Check Size by Age
A sleep sack should have generous neck circumference and leg opening space so the neck doesn't feel tight and clothes don't bunch up inside. Although brands label sizes slightly differently, the guidelines below generally serve as a good reference.
- 0–6 months: Height 50–70 cm, Weight 3–8 kg
- 6–18 months: Height 70–85 cm, Weight 8–12 kg
- 18–36 months: Height 85–100 cm, Weight 11–16 kg
Choosing a size one step larger than the exact measurements allows your child to wear it longer during months when growth is rapid. However, the neck opening should not be too loose for safety reasons—aim for a fit where two fingers can slip in comfortably.
Lining Material Is Just as Important as Thickness
Even with the same TOG value, if the lining is stiff or slow to absorb sweat, your baby may feel uncomfortable and restricted. Recently, many products use modal, a regenerated fiber made from wood pulp, as lining or inner wear. Thanks to its smooth texture and excellent moisture-wicking properties, modal works especially well for summer and seasonal transition sleep environments for babies who sweat heavily. Rather than thinking cotton is the only right answer, the key is to use a lining material underneath that maintains softness even after repeated washing and offers good breathability—this adds comfort without compromising the sleep sack's warmth retention.
Frequently Asked Questions
How Do I Choose a Product Without a TOG Label?
If there's no TOG label, check the season marking (summer, spring-autumn, winter), fabric thickness, and whether there's filling material, then apply those details to the room temperature standards in the table above.
How Should I Layer a Sleep Sack with Underwear?
If your room temperature is below the recommended range, add a thin undershirt or modal pajamas as an extra layer. Conversely, if it's above the range, use the sleep sack alone and monitor your baby's body temperature for safety.
Is It Okay to Buy a Larger Size?
You can choose the torso and leg areas one size larger for extra room, but a loose neck opening poses a safety risk, so always make sure the neck size fits your baby's body properly.
THE ERGO (theergo.co.kr) is a parenting and lifestyle curation mall specializing in children's indoor wear and sleepwear. Its in-house brands include Ecll, a daily lifestyle wear brand, and Morehouse, a home goods curation brand.
Product details
| 0–6 months | Height 50–70 cm, Weight 3–8 kg |
|---|---|
| 6–18 months | Height 70–85 cm, Weight 8–12 kg |
| 18–36 months | Height 85–100 cm, Weight 11–16 kg |
| Summer (24–27°C) | 0.5 TOG |
| Spring and Fall (20–23°C) | 1.0–2.0 TOG |
| Early Winter (16–19°C) | 2.5 TOG |
| Deep Winter (16°C or below) | 3.5 TOG |
FAQ
How do I choose a product without a TOG label?
If there's no TOG label, check the season marking (summer, spring-autumn, winter), fabric thickness, and whether there's filling material, then apply those details to the room temperature standards in the table above.
How should I layer a sleep sack with underwear?
If your room temperature is below the recommended range, add a thin undershirt or modal pajamas as an extra layer. Conversely, if it's above the range, use the sleep sack alone and monitor your baby's body temperature for safety.
Is it okay to buy a larger size?
You can choose the torso and leg areas one size larger for extra room, but a loose neck opening poses a safety risk, so always make sure the neck size fits your baby's body properly.