How to choose a sleep sacks
Updated June 2026Independently researchedNo paid placement.
Choose a sleep sack by matching the TOG rating to your room's temperature, selecting the correct size for your baby's weight and height, and prioritizing safe design features like a snug fit around the chest and a zipper cover. Always check that the sack allows for hip-healthy movement and is made of breathable, natural-fiber material when possible.
What TOG rating do I need for my baby’s sleep sack?
TOG (Thermal Overall Grade) measures how well a sleep sack insulates. Lower TOG ratings (such as 0.2 or 0.5) are for warm rooms or summer nights, while higher ratings (2.0 or 2.5) are for cooler nurseries in winter. Many brands offer a 1.0 TOG sack as a versatile year-round option when paired with appropriate pajamas. To choose correctly, keep a room thermometer near the crib and dress your baby in the sleep sack appropriate for that temperature. Most sleep sack brands provide a temperature guide on their packaging or website. If the room stays between roughly 68 and 72 degrees Fahrenheit, a 1.0 TOG sack with a short-sleeve onesie often works well. For rooms above 75 degrees, a very lightweight or no sack may be safer.
How do I find the right size sleep sack for my baby?
Sleep sack sizing is based on weight and length, not just age. A sack that is too large can ride up over your baby’s face, while a sack that is too small can restrict movement or be uncomfortable. Always follow the manufacturer’s weight range and check that the armholes and neck opening fit snugly without gaping. Most brands offer sizes from newborn through toddler, often overlapping at the transition points. Measure your baby’s height and compare to the product’s recommended height range. A good rule is that your baby should be able to move their legs freely inside the sack but not have so much extra fabric that it bunches around their chest.
What materials are best for baby sleep sacks?
Cotton, bamboo, and cotton-bamboo blends are popular because they are breathable, soft, and gentle on sensitive skin. Organic cotton sacks are widely available and avoid pesticide residues that might irritate some babies. Fleece and microfleece sacks provide warmth but are less breathable, so they are best for cooler rooms and should not be layered over heavy pajamas. Wool sleep sacks are another option for temperature regulation and moisture-wicking, but they tend to be more expensive and require careful washing. Regardless of the fabric, check that the material is labeled as flame-retardant-free or meets safety standards without chemical treatments.
What safety features should I look for in a sleep sack?
The most important safety feature is a secure fit around the chest and under the arms. The sack should not allow your baby to slip down inside it. Look for a design with a zipper that starts at the bottom or has a zipper cover to prevent skin irritation. Some sleep sacks have inverted zippers that zip downward, making diaper changes easier without fully undressing your baby. Another key feature is a design that does not restrict hip movement; the sack should allow your baby’s legs to fall into a frog-like position. This supports healthy hip development, especially in the first few months. Also, avoid sleep sacks with hoods, extra padding, or loose ribbons or buttons, which can pose choking or entrapment risks.
How should I dress my baby under a sleep sack?
The rule is simple: use one more layer than you would wear comfortably in the same room. For a 1.0 TOG sack in a moderately cool room, a long-sleeve footed sleeper is usually sufficient. In a warmer room, a short-sleeve onesie or just a diaper may be enough. Never add a blanket on top of the sleep sack, as this can cause overheating. Always feel your baby’s tummy or the back of their neck to check their temperature, not their hands or feet. If the skin feels hot or sweaty, remove a layer. If the chest feels cool, add a layer or choose a higher TOG sack. Overheating is a known risk factor for SIDS, so err on the cooler side.
Frequently asked questions
Can I use a sleep sack together with a swaddle?
No, once your baby shows signs of rolling over, you should stop swaddling and transition to a sleep sack. Some sleep sacks are designed as wearable blankets that allow arm movement, while others have enclosed wings for a swaddle-like feel. Once your baby rolls, only use an arms-free sleep sack.
How do I tell if my baby is too hot or too cold in a sleep sack?
Check the nape of the neck or the tummy. If the skin feels damp or hot, your baby is too warm; remove a layer or choose a lower TOG sack. If the skin feels cool to the touch, add a layer or increase the TOG rating. Do not rely on hands or feet, which often feel cool even when the baby is comfortable.
Can sleep sacks be used for naps as well as nighttime sleep?
Yes, sleep sacks are safe for all sleep periods, including naps. Consistency in using the same sleep environment, including a wearable blanket, can help cue your baby that it’s time to sleep. Just always place your baby on their back on a firm, flat surface.
How do I wash a sleep sack without damaging it?
Always follow the care label, but most cotton and bamboo sleep sacks can be machine washed on a gentle cycle with cold water and tumble dried on low heat. Avoid fabric softeners and bleach, which can break down the fibers and reduce breathability. Fleece and wool sacks may require special handling, such as hand washing or air drying.
When should my baby stop using a sleep sack?
There is no set age to stop, but many children transition to a lightweight blanket or a sleep bag once they can climb out of the crib, typically around 18 to 24 months. Some sleep sacks are designed for toddlers up to 36 months or 40 pounds. Use your child’s mobility and crib-safety measures as your guide.
What’s the difference between a sleep sack and a wearable blanket?
The terms are often used interchangeably. Both are sack-shaped garments that cover the body and are secured with zippers or snaps. Some brands distinguish them by TOG rating or arm-style, but functionally they serve the same purpose: to keep your baby warm without the risk of loose bedding.