Knitting Blog

The Secret Formula for Knitted Baby Hats That Fit Every Time

Whether you’re knitting hats to donate to babies in the NICU or for people you love, hats are a great, practical gift for babies and new parents. One of the trickiest parts of knitting for babies is sizing. When I had my first baby, I had a hard time figuring out what clothes he would need in each size per season. Would a baby born in the spring need 6- or 9-month clothing in the winter?  Some babies are big and some babies are small, and baby’s heads grow the fastest in the first year.  How will you know what size will fit best?

Cabled Baby Hat Knitting pattern

My Muse Cowl & Hat Baby Size pattern by Craftsy member Lyudmyla Vayner

To help you whip up baby hats of all sizes, here is a little chart to help you determine what size hat you’d like to make so you don’t end up making a hat too big or too small when winter rolls around.

Average baby head measurments by size

  • Preemie head size: 9-inch circumference and 4 inches tall
  • Newborn size: 11-inch circumference and 5 inches tall
  • 0-3 month size: 13-inch circumference and 6 inches tall
  • 3-6 month size: 16-inch circumference and 7 inches tall
  • 6-9 month size: 18-inch circumference and 7.5 inches tall
  • 12 month size: 20-inch circumference and 8 inches tall
  • 24-4T size: 21-inch circumference and 8.5 inches tall

Using the above sizing information, here is the formula to determine how many stitches you need to cast on in the round to knit that baby hat size:

Circumference (in inches) x stitches per inch = cast on number

If you’ve knit several baby hats before, you can use the above formula with any weight of yarn and appropriate needle size. Knit until you get half an inch shorter than the desired hat. Bind off by k2tog every five stitches until you have one stitch left on your needles. Then, pull the yarn through the last loop and weave in the ends to your hat.

You may need to increase (every two stitches k2tog) or decrease (every 10 stiches k2tog) the number of stitches you need to knit together as a decrease depending on the yarn you’re using.

What size baby hat should you knit?

  • For a baby due in the spring, knit a size 6-9 month to wear this year, or a size 18-24 month for next year.
  • For a baby due in the summer, knit a hat in 3-6 month size to wear this year, or 18-24 month for next year.
  • For a baby due in the fall, knit a hat in 0-3 or 3-6 month size to wear this year, or 24-month size for next year.
  • For a baby due in the winter, knit a hat in 0-3 or 3-6 size to wear this year, or 12-month or 24-month size for next year.

FREE baby hat knitting patterns

If you’d like a pattern that involves less guesswork, try one of these free patterns from Craftsy designers.

One Hour Baby Toque

Photo via Craftsy member Purl and Company

One Hour Baby Toque

Only have a day or two to whip up a sweet gift for a new baby? This pattern uses super bulky yarn, you’ll have it done in a flash. Since the pattern has no fancy stitches, it’s easy to adjust the size so it fits your kiddo perfectly.

Get the FREE pattern »

Cascade Jewel Beanie for Babies

Photo via Craftsy member BrianaKCrochet

0-3 Month Cascade Jewel Beanie

This pattern is designed for babies fewer than 3 months old — but now that you know how to pick the perfect size, you could easily adjust it to fit any child. Bulky yarn makes these hats super soft (and super quick to make).

Get the FREE pattern »

Pumpkin Spice Pom Pom Knitted Hat

Photo via Craftsy member Lyudmyla Vayner

Pumpkin Spice Pom Pom Knitting Pattern

Have you ever seen a hat cuter than this one? The pom poms are irresistible! Orange and brown makes for a great fall color palette, but this pattern would be equally adorable in any other color combo. Plus, if you haven’t wrapped your head around the math for measuring hats, this pattern helps you calculate the right size.

Get the FREE pattern »

Top Baby Hat Knitting Patterns

baby hat knitting patterns

Explore popular baby hat knitting patterns from the world’s best designers.Get Patterns Now »


Lyudmyla Vayner/ LyudmylaKnitDesigns

Dear Ashley Martineau – awesome article – thank you! Quick note re the decrease portion math for the hat – in my experience, it’s usually the crown size is not about 0.5 inches – but closer to the 1/3 of the hat full length. Hope this helps!

Lyudmyla Vayner / LyudmylaKnitDesigns
P.S.: Many thanks for featuring my little girl and my two hats in your blog!


thank you so much for this very good information! : )


Would you have a pattern for a babies knitted or crochet cap for 6th old baby boy


THANK YOU! This is 100% helpful!!! THANK YOU!


Good Morning I have 1 Skein of Variegated Fixation Yarn by Cascade ( 98 % Cotton, 1% Spandex. I want to Knit a HAT for a 4 year old Boy who is going thru Chemo and Radiation. I am a tight Knitter. Do you have patterns for 4 year old? I didn’t see any on your page. His Head measurement is between 20 and 21 inches. I have never knitted a hat so I do not know how stitches and needles to use. Thanks.


Good Morning I have 1 Skein of Variegated Fixation Yarn by Cascade ( 98 % Cotton, 1% Spandex. I want to Knit a HAT for a 4 year old Boy who is going thru Chemo and Radiation. I am a tight Knitter. Do you have patterns for 4 year olds? I didn’t see any on your page. His head measurement is between 20 and 21 inches. I have never knitted a hat so I do not know what stitches and needles to use.

Can you please help me?


I left 2 comments but they are not being posted here. How come!!



I would love the link to the grey cap in the Top Baby Hat Knitting Pattern box. I can’t find it on the site – it’s a lot to look through! Thanks

Abdul salam

What diameter of hat is ideal for a 1 year old baby…normal head size


I want to say thanks to the author for the detailed numbers! I would also like to say if you read what is put out there and chew on it a bit, you will have the answers to your own questions in most cases….BUT I am with Cheri…the grey one is too darn cute…gotta make it!…guess I will dig thro the stack and see if I can take my own advice!

Myla Vayner

would you please update designer’s name for My Muse and Pumpkin Spice – should be Myla Vayner – and the link to My Muse is not working – could you please fix it?

both are FREE patterns:)

thank you!


I make hats for a NICU-little itty bitty ones -Love it !!!


I would love a link to the pattern for the little gray hat So cute!


Thank you so much for the above information. I’v knitted for many years. I will have a grandchild in January so this is invaluable to me. I won’t have to guess which will be such a blessing.
I’m really thrilled!!!
Thanks so much!!!!!!!


Hi i just want to ask about tulip i use 3.0mm and im confuse if how many stitch i make so that i can make for the baby beanie kindly please help me im beginner to make crochet thank n godbless..


Thanks for the super info, great article.
I tried to download the free Pumpkin Spice PomPom patern, but it’s not free.
If it is free and I’m missing something like a coupon code please let me know because the website does charge for this pattern.
Thanks again!


For a newborn hat- if a typical newborn’s head is 5” tall, at what length would I need to begin finishing the hat? And how does that work for other head heights? That’s what confuses me. I understand how to know how many stitches to cast on, just not how to get the correct hat height. (This is in going by your measurement chart, for simplicity’s sake.) Also, do you need to make the hat a certain amount taller than the head height, or if the head height, like for a newborn, is 5 inches, do I just begin finishing the hat off at 4 1/2 inches.

Thank you!


I was super thrilled to see this chart since I need to make a hat for my father-in-law to give to my one year old niece, I know sounds funny, I did a swatch, measured and started my hat. Sadly about 1/2″ in I knew it was too big, so I worked it off onto some yarn… and I could get it on my own head, no I don’t have a small head, and yes, I used the same needless and yarn as the swatch and I’ve been knitting for about 15 years. Some research and everywhere I looked, both medical sites and other knitting sources showed circumferences of one year old children between 17 1/2 to 18″, not the 20″ given here, which on my sticks/yarn is about a12 stitch difference… And that’s not even considering stretch, which in many hat cases you’d want. Looks like if I took out at least those 12 stitches the diameter is about right, so your math seems right, it’s just the one year old circumference that may be wrong. Either way, thanks for your work figuring out that bit math.


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