Merino Wool Infant Sleep Sack

After Calvin was born I was looking for a sleep sack, and came across this one on Amazon. After doing some research about Merino wool I was hooked. But, I didn't want to spend over $100 on a sleep sack. So my very smart and practical husband suggested "Why not make your own?"

I wouldn't say it is as inexpensive as buying a sleep sack from Wal-Mart, but it's definitely a lot less money than buying a Merino wool sleep sack from an online store!

After using a wool sleep sack I've noticed that Calvin sleeps much deeper. He still wakes once or twice to eat during a 12 hour period, but his sleep is restful and deep. Before the sleep sack he was pretty restless at night, and I suspect it was because he was uncomfortable.

The $45 and 3 hours it took to make the sleep sack has been well worth it. I love that when I unzip the sleep sack Calvin's feet are warm and dry. When Sawyer and Calvin wear fleece footie pajamas their skin gets hot and clammy, I'm sure it's very uncomfortable to feel that hot and stifled. Sawyer regularly will wake up in the night and make us take off his fleece PJs and replace them with cotton ones, but then he gets cold later on because he's not good at keeping the blanket on. The struggle is real!
I am trying to drum up the motivation (and skills) to make him some Merino wool pajamas. I am also going to attempt to make a swaddle blanket for a newborn, but that won't be for a while.

Before I get into making a wool sleep sack, I'm going to talk about why you need one :) if you aren't sold by the end, then I'm a terrible salesman. By the way, I'm not endorsing any one product, my passion for Merino wool comes from personal experience only.

Regulates Body Temperature and Wicks Moisture

Infants do not developed the ability to adapt to temperature changes as well as adults can and heat is lost from their little bodies up to 4 times faster. 

Merino has a natural ability to help the baby maintain a constant body temperature. It will absorb and release moisture away from baby’s body to keep baby cool when it is hot, or trap and circulate warm air to keep baby warm when it is cold.

Helping baby be more comfortable through the night helps baby have a deeper and more restful sleep. This way babies preserve their energy for growth and development. That's why studies have shown that babies swaddled in Merino wool gained more weight than babies not swaddle in Merino wool.

Merino fibers and fabrics can absorb up to 30% of their dry weight before feeling wet. Most synthetics feel wet after they absorb less than 7%.

Fire and UV Resistant 

Merino wool is self-extinguishing and it never melts. I love that it is free of chemical fire-retardants and I that I can feel safe knowing that my baby's skin is safe if there ever was a fire, and safe sleeping every night not soaking in lots of chemicals!
In fact, it is so fire resistant and excellent at temperature control, that a fire department in the UK is using Merino wool as base layer for their fireman.

Antibacterial and Anti-Odor

Since the wool fibers wick away and absorb moisture it makes it impossible for mold, fungi, and bacteria to grow. Sheep naturally make an oil called lanolin (you nursing moms may have heard of this wonderful stuff before!), which waterproofs the wool and reacts with urine to neutralize it, creating a by-product of water and salt. I've used wool cloth diaper covers with Sawyer and Calvin and I am constantly amazed at the power of wool and lanolin. I will use a cover for 2 weeks and it still smells as fresh as the day I washed it. Seriously, it's mind-boggling!

Durable and Sustainable

Merino wool fibers can be bent 20,000 times before breaking. By comparison, a cotton fiber will break after 3,000 times and silk after just 2,000.
The more I learn about farming practices and the environment the more firm my resolve to make more eco-friendly choices.
So I love the fact that wool is a renewable source, and it does no harm to the animal, or the environment. It also does not require mass amounts of pesticide (unlike cotton which is responsible for 16-25% of the worlds pesticide use). And it's biodegradable, so when it's given up the fabric-ghost you can throw it in your compost pile, if you so desire :)

All this stuff may seem gimicky, but if you think about the fact that sheep can stay warm and cool despite the weather and seasons, and their wool stays clean and dry without soap or waterproof jackets, it isn't so gimicky after all. To me, it's a testament that our loving Heavenly Father not only created sheep in a way that they can live comfortably in their environment, but that he gave us something wonderful to use for clothing that doesn't cause the animal or the environment any harm. Isn't it neat?

Alright, now that you are going to go out and buy Merino wool fabric to make your babies, grandbabies, friends' babies (and maybe even yourself)  a sleep sack, here's how to do it (plus the amount it cost me to make mine).
If you aren't crafty or just don't have the time to make one, you can buy one from Superlove Merino, Merino Kids, Woolino, and many other places. I even found some on Ebay and Craigslist! They were about $75, but still cheaper than buying new.

Find a Pattern |  $7

There are a ton of free patterns for sleep sacks, but I wanted one that had the zipper on the side, and I wanted detailed instructions and pictures so I didn't mess up my wool fabric. I ended up choosing this one because it had a good pattern and instructions.

Buy Merino Wool | $22

I only needed 1 yard of lining  for the pattern I chose, and I bought it from NZ Wool and Fabrics. The price per meter/yard was fairly reasonable, about $16 USD. The problem is that shipping from NZ costs about $6/yd so the price per yard ends up being a little pricier than simple cotton fabric. But considering that other companies charge $50+ per yard, this was more than reasonable.
I wrote the owner and she said you want the fabric weight to be about 200g, give or take. I used 190g for my first sleep sack, and the second I used 210g. You can definitely feel a difference in weight. The 190g would be PERFECT for a newborn swaddle blanket because it's light and very stretchy. I only needed a yard for each sleep sack, so it's not too bad. The 190g would also be great if you live in a very hot climate.

Buy Outer Fabric | $5-15

If you want a pure wool sleep sack, you can sew Merino wool on the inside and outside. I wanted a cute pattern so I opted for an organic cotton for the outside fabric. Before you choose a fabric, read about different knit fabrics to avoid getting the wrong kind. I prefer knit interlock because it easier to sew and has less stretch. The brands below have the cutest prints and they are thick, high-quality fabrics. I bought some clearance knit fabric at Joann's, but it was already pilling before I even sewed it. So I went for the higher-quality fabrics instead. The sack I made a few months ago is still in great shape and I'm glad I made the splurge.
Birch Organic Knit Cotton
Art Gallery Knit
Cloud 9 Organic Knit Cotton

Buy Hardware | $5-10

You need an invisible zipper, which will cost about $4 from Joann's, but you could easily make that $2 with a coupon. You also need buttons or snaps. I used snaps, but buttons would work just as well. In fact, the pattern I bought recommends buttons because they last longer.

You may want to purchase some wool cleaner, like this. Although I don't think it's absolutely necessary, it will help it last longer and keep it waterproof.

Be Extra Frugal!

You can also look in the clearance section of the NZ online store and find something that works, you need about 100 cm for the sleep sack, FYI.
If you position your pattern efficiently on the fabric you should have enough leftovers to make 1-2 baby drool bibs/bandanas. Here is my favorite pattern for a baby bandana. I've made 4 from my fabric leftovers, one side cotton and one side Merino wool. They are great for drooly babies :)

More information about Merino wool:
The Super Wool - Superlove Merino Wool
List of Research Studies - Superlove Merino Wool
Merino Wool, Firemen's Choice for Base Layer
Smart Wool


  1. Hi Jessica,
    I'm inspired by your post and I'm planning on making a similar sleep sack. My question to you before I purchase the wool is: are you happy with how the cotton/wool sack turned out or would you do a 100% wool sack of you could do it over again? The lady I spoke with at NZ Merino recommend using all wool but I love the idea of a cute cotton pattern. Is yours warm enough? We keep our house around 68-70 degrees at night. Thanks! Beautiful sleep sack!

  2. Hi, where could I find the pattern that you used?

  3. Hi, I'm struggling to find a pattern with the zipper at the side. Could you please share where did you get your pattern from? Thanks, AMAYA.

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