The right baby sleeping bag size for maximum comfort

Your baby is growing, and you're wondering which sleeping bag size to choose? Between 70, 90 and 110 cm sleeping bags, the age recommendations on labels and the differences between brands, finding the right fit isn't always straightforward.

At Zizzz, the 70 cm sleeping bag is generally suitable from birth to 6 months, the 90 cm sleeping bag from 6 to 24 months, and the 110 cm sleeping bag from 24 to 48 months. Larger sizes are also available for older children who enjoy continuing to sleep in a sleeping bag.

But remember: age is only a guideline. The most important thing is to choose a sleeping bag that fits your child's body properly, with a snug but comfortable neckline and enough room to move freely.

Baby Sleeping Bag Size Guide by Age

Here are the Zizzz sleeping bag sizes and the ages they are generally designed for:

Age recommendations can vary between brands. A 65 cm or 80 cm sleeping bag, or a size labelled "T1" or "T2", may correspond to different age groups depending on the manufacturer.

It's therefore better to consider the length in centimetres and your child's actual size rather than relying solely on the age printed on the label.

How Do You Calculate the Right Sleeping Bag Length?

To estimate the appropriate length, some health authorities recommend a simple formula:

Your child's height − the length of their head + approximately 10 cm

The additional 10 cm provides room for your child to move their legs and allows a little space for growth.

However, this formula is only a general guideline. The length advertised by manufacturers doesn't always correspond exactly to the usable internal length of the sleeping bag.

When choosing a Zizzz sleeping bag, start with our size guide, then check that the neckline and shoulders fit properly and that your child has plenty of room to move their legs comfortably.

What Size Sleeping Bag Is Best for a Newborn?

At Zizzz, the 70 cm sleeping bag is designed for babies from birth to approximately 6 months, depending on their growth.

Always check that the neckline and armholes fit your baby's body properly. For premature or particularly small babies, a smaller, more suitable sleeping bag may be necessary.

Zizzz sleeping bags feature an adjustable neckline with poppers. If your baby's head or arms can slip inside the sleeping bag even when the neckline is adjusted to its smallest setting, the sleeping bag is still too large.

How Can You Tell if a Baby Sleeping Bag Is Too Big or Too Small?

Choosing the right size isn't just about checking the length. The sleeping bag must also fit comfortably around your baby's shoulders, chest and neck.

Signs That a Sleeping Bag Is Too Big

• The neckline remains too wide, even at its smallest setting, and your baby's head could slip inside.
• Your baby's arms can slip through the armholes into the sleeping bag.
• Excess fabric creates large folds around the shoulders and chest.

Buying a sleeping bag that's too big isn't a good way to prepare for future growth.

The UK's Lullaby Trust stresses that a baby sleeping bag should fit securely around the shoulders to prevent the baby's head from slipping inside.

Always choose a sleeping bag that fits your baby now, rather than buying a larger size for them to grow into.

Signs That a Sleeping Bag Is Too Small

• Your child no longer has enough room to bend, stretch and move their legs freely.
• The sleeping bag pulls at the shoulders or feels tight around the chest.
• The neckline is too tight, even when adjusted to its widest setting.

Neckline and Armholes: What Should You Check?

The neckline should be narrow enough to prevent your baby's head from slipping inside the sleeping bag, but never tight around the neck.

A useful guideline is that one adult finger should fit comfortably between your baby's neck and the neckline.

The armholes should also fit closely enough to prevent your baby's arms from slipping inside. There should be no ties or cords around the arms.

An adjustable neckline makes it easier to adapt the sleeping bag as your baby grows.

Zizzz sleeping bags have poppers around the neckline to adjust the opening, along with a zip that allows you to change your baby's nappy during the night without having to remove the sleeping bag completely.

If you're wondering whether a sleeved or sleeveless model would be more suitable, take a look at our article on baby sleeping bags with or without sleeves.

When Should You Move Up to the Next Sleeping Bag Size?

It's time to move up to the next size when your child no longer has enough room to stretch their legs freely, the sleeping bag pulls at the shoulders, or it becomes too tight around the chest.

With Zizzz sleeping bags, this generally happens:

• Around 6 months: moving from 70 cm to 90 cm.
• Around 2 years: moving from 90 cm to 110 cm.

However, every child grows at their own pace.

Growth spurts may mean your baby needs a larger sleeping bag several weeks earlier than expected, so it's worth checking the fit regularly.

Before using the next size, always make sure the neckline and shoulders fit properly.

Until What Age Can Children Use a Sleeping Bag?

There's no fixed age limit for sleeping bags.

Many children continue using them well beyond the age of 2 or 3 because they enjoy the familiar feeling and don't kick off their covers during the night.

That's why Zizzz also offers larger sleeping bags:

• 130 cm sleeping bags for children aged approximately 4 to 6 years.
• 160 cm sleeping bags for children aged approximately 6 to 10 years.

The right time to switch from a sleeping bag to a duvet depends mainly on your child.

Some children are happy to make the change earlier, while others prefer to continue using their sleeping bag for longer.

When your child expresses an interest in sleeping under a duvet or seems ready to manage their covers during the night, it may be time to consider the transition.

We explore this topic in more detail in our article When Should Your Child Stop Using a Sleeping Bag?

Which Sleeping Bag Thickness Should You Choose for Your Baby's Room Temperature?

Size isn't the only factor to consider. The thickness of your baby's sleeping bag should be appropriate for the temperature of the room, rather than simply the season.

The Lullaby Trust recommends a room temperature of 16 to 20°C for babies.

At Zizzz, we offer different types of sleeping bags to suit different temperatures:

• Zizzz 4-Season Sleeping Bag: made with organic cotton and natural Swisswool filling. Zizzz indicates a recommended room temperature range of 16 to 22°C for this model. This is the brand's intended usage range, not a universally ideal temperature for every baby.
• Zizzz Summer Sleeping Bag: made from a single layer of organic cotton, offering a lighter option for warmer nights.

The clothes your baby wears underneath the sleeping bag should also be adapted to the room temperature and the warmth of the chosen model.

Depending on the conditions, a vest or sleepsuit may be sufficient.

Check your baby's neck or chest regularly to make sure they aren't too hot or too cold. If their skin feels hot or damp, remove a layer of clothing.

It's normal for babies to have slightly cool hands and feet, so these aren't always reliable indicators of their overall temperature.

To learn more about the insulation ratings used by many sleeping bag manufacturers, read our article on TOG ratings for baby sleeping bags.

What Is the Best Material for a Baby Sleeping Bag?

When choosing a baby sleeping bag, look for breathable materials that allow air to circulate and manage moisture effectively.

Babies and young children can become warm and sweaty during the night, so it's important to choose fabrics that help maintain a comfortable sleeping environment.

Zizzz sleeping bags are made with GOTS-certified organic cotton and natural Swisswool filling.

Our Swisswool filling consists of:

• 88% Swiss sheep's wool
• 12% plant-based fibres, which help make the filling machine washable.

Wool naturally absorbs moisture and helps regulate temperature, making it a particularly suitable material for baby sleeping bags.

Polyester, which is commonly used as a filling material, absorbs significantly less moisture than wool.

Both materials have different properties, which we explore in more detail in our article Wool vs. Polyester Baby Sleeping Bags: Which Is Better?

Frequently Asked Questions About Baby Sleeping Bag Sizes

What Age Is a 70 cm Sleeping Bag Suitable For?

At Zizzz, the 70 cm sleeping bag is designed for babies from birth to approximately 6 months.

Age recommendations may vary between brands, even for sleeping bags of the same length.

The most important thing is to make sure your baby has enough room to move their legs freely and that the neckline fits securely.

What Age Is a 90 cm Sleeping Bag Suitable For?

The Zizzz 90 cm sleeping bag is generally suitable for babies and toddlers aged 6 to 24 months.

Move up to the next size when your child no longer has enough room to stretch their legs freely, the sleeping bag pulls at the shoulders, or it becomes too tight around the chest.

What Age Is a 110 cm Sleeping Bag Suitable For?

The Zizzz 110 cm sleeping bag is generally suitable for children aged 24 to 48 months, or approximately 2 to 4 years.

For children over 4 years old, Zizzz also offers a 130 cm sleeping bag.

Is It Dangerous if a Baby Sleeping Bag Is Too Big?

A sleeping bag that is too large is not recommended.

If the neckline or armholes are too wide, your baby's head or arms could slip inside the sleeping bag.

Always choose a size that fits your baby's current height and body shape rather than buying a larger sleeping bag for future use.

How Many Baby Sleeping Bags Should You Buy?

We recommend having two 4-season sleeping bags in each size.

Swisswool sleeping bags are machine washable, but they take some time to dry.

They should generally not be tumble-dried unless the care instructions specifically allow the use of a suitable wool-drying programme.

Having a second sleeping bag available means you'll always have a clean one ready while the other is being washed or dried.

For more advice, read our article How Many Baby Sleeping Bags Do You Need?

Sources

• Ministry of Labour, Health and Social Affairs of North Rhine-Westphalia (MAGS NRW) – Safe Baby Sleeping Bag: recommendations on sleeping bag length, neckline and armhole fit.
• National Child Mortality Database (NCMD) – Baby Sleeping Bags: What to Consider: guidance from the Lullaby Trust on sleeping bag sizing and ensuring a secure fit around the shoulders.
• The Lullaby Trust – Baby Room Temperature: recommended bedroom temperature and advice on checking whether your baby is too hot or too cold.