Sleep Sack Sizing

Sleep Sack Sizing

Get the Right Sleep Sack Size

The infant phase is as magical as it is, well, tiring. Luckily, there are sleep solutions to help your baby (and you) get more rest. Among the most helpful items in a sleepy-time arsenal are weighted and non-weighted sleep sacks. These sleep essentials mimic the same comfort to your baby as they experienced in the womb. Snug and warm, just like a hug - but, when is snug too snug, and are sleep sacks safe if they're too loose? It’s all about finding the right fit in order to benefit from their seemingly magical powers while keeping safe sleep a top priority. Keep reading to learn all about sleep sacks, including how to find the best fit for your little one, how to dress your baby underneath a sleep sack, and more. 

How do I get the right sleep sack size?

To get the best fit for your baby’s sleep sack, purchasing the appropriate size is crucial. Most sleep sacks come in various sizes for age ranges, such as our Dream Weighted Sleep Sack and our non-weighted Bamboo Classic Sleep Sack, which are available for age ranges: 0-6 months, 6-12 months, 12-24 months, and 24-36 months.

 Other brands may opt for small, medium, and large sizing or different age ranges. It is important to keep in mind that each brand may have different specs when it comes to height and weight ratios for correlating sizes. It’s also important to remember that babies can vary in size, too. 

Referring to a size chart is the best way to take the guesswork out of shopping for a new sleep sack. When determining the right size sleep sack for your baby or toddler, keep their individual growth patterns and mobility needs in mind - especially if they are between sizing. 

How do I know if my baby's sleep sack fits?

When checking for proper fit, it is important to maintain balance between secure fit and eliminating the risk of discomfort or hazards. Your baby’s Goldilocks of sleep sack sizing will be a fit where the arm and neck holes fit snugly, but not too snug. 

When dressing your baby in a sleep sack, their arms should slip through the arm holes without any struggle. Ensure that your baby has plenty of space to move their limbs and neck freely, without any baggy fabric.  The body of the sleepsack should fit snugly so that your baby’s body doesn’t get entangled or lost in the fabric as they wiggle around. The key thing to remember about finding the best sleep sack fit is: snug but not tight.

How tight should a sleep sack be on a newborn?

Part of the reason why sleep sacks help your little one sleep so well is because that snug fit gives babies, especially newborns. It resembles the calming security that they had in the womb. Because newborns are especially delicate, finding the best fit is crucial. A sleep sack that fits too tightly on a newborn can not only be uncomfortable for them, but can be a safety risk as well. An excessively tight sleep sack can interfere with proper breathing and even disrupt healthy circulation. On the other hand, a sleep sack that fits a newborn baby too loose can easily shift to cover their nose and mouth with little movement. Again, snug - but not tight

Is it OK if the sleep sack is a little big?

If your baby is between sizes or you’re aiming for longevity of use, it is okay if your baby’s sleep sack is just a little bit big. A size that leaves a little room to grow is okay - as long as it passes the “fit test.” 

  1. Place the sleep sack on your baby.
  2. Quickly pull the neckline of the sleep sack over the area of your baby’s mouth and nose (without closely covering them).
  3. Let go.

Did the fabric of the neckline snap back below the baby's chin? Congratulations, your baby’s sleep sack has a safe fit. If the fabric remains hovered over their mouth and/or nose, it’s time to hang that sleep sack back up for a few weeks before testing the fit again. 

When should I change my sleep sack size?

As we all know, babies grow very quickly. What may fit them well on Tuesday can seem way too small by Friday. Older babies and toddlers may have an easier time letting you know that their sleep sack isn’t as comfortable as it once was. However, you may have to pay more attention to smaller babies when they may be coming to the end of their sleep sack’s life. It might be time to change your sleep sack size if your baby begins waking more frequently, wiggling around to get comfortable, if their feet push on the bottom seam, or if the neck and armholes appear too tight. 

Are babies supposed to wear clothes under their sleep sack?

Now that we have sizing down, let’s talk about how to dress your baby under their sleep sack. Babies can definitely wear clothes under their sleep sack, but keep in mind that thick or baggy clothes may affect proper sleep sack sizing. It is also important to keep temperature in mind when dressing your baby for sleep as overheating can be a risk factor for SIDS (sudden infant death syndrome). If the weather is warm, your baby might be more comfortable (and safer) in just a diaper and their sleep sack. Thin onesies may be appropriate as well. When the weather isn’t too warm, your baby can be comfortable and safe with pajamas under their sleep sack. Fabrics such as breathable cotton and temperature-regulating bamboo can help ensure the best, and safest, sleep. Shop our Dream Pajamas made with 100% breathable cotton or our Baby Bamboo Pajamas that pair perfectly with our best-selling sleep sacks. 


Although finding the right fit is crucial for comfort and safety, it doesn’t have to be hard. Whether you’re looking for a standard Weighted Sleep Sack for deep pressure stimulation to help your baby drift off to dream land, or the buttery softness of a non-weighted Bamboo Classic Sleep Sack - we make finding the right size easy. Size charts are  located on any of our product pages. If you ever find yourself with additional sizing questions, you can always reach customer support at [email protected]. At Dreamland, we love sleep, so don’t let the worry of your baby’s sleep sack sizing keep you up at night. Reference our size charts, take advantage of our simple designs, and reach out to us for help.

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In June 2022, the AAP updated its sleep guidelines and is currently not recommending weighted sleep solutions. You can read the full report here. Please note that this is not a recall. Dreamland Baby is in ongoing dialogue with the AAP regarding its stance on weighted sleepwear and hopes it will result in the statement being retracted.