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A Guide to Hat Sizing
Combining feedback from the Head Measuring Game with my decades of Hat knitting experience, I developed this sizing guide to help all Hat knitters and crocheters. This information was originally available as a static page on my former website, and was converted to a blog post in 2009 so that I could offer help via the comments.
This page will help you obtain accurate head measurements for babies, children and adults, and in turn help you choose the right size for the perfect fit.
Head sizes vary from person to person, but generally fall into the size categories below. To be sure though, one size does not fit all, or even most!
Getting Started
To measure your head circumference, wrap a tape measure around the widest part of your head – over your hair, starting from your forehead, above your ears and around the back, then round to the front again.
Make sure the tape measure is snug – a Hat should fit snuggly; not too tight or too loose. The circumference is the measurement used for Hat sizes, and is the measurement given for the brim of the Hat.
The length of a Hat will vary between styles, but to know the length of your head in relation to the pattern, measure from your crown to the base of your ear and this will give you your ideal head length for Hats.
Hat patterns contain measurements and sizing based on gauge, and number of stitches and rows – if your working gauge is tighter or looser than that given, you may need to adjust your number of stitches accordingly, or adjust your needle or hook size.
Diagram 1 shows arrows indicating both directions we need to measure
Choosing the Right Size
The finished measurements for Hats listed in the patterns may be slightly smaller than those given below, to ensure the fabric is stretched slightly for a snug fit – this is known as ‘negative ease’. The actual difference between the finished size of a Hat compared to the desired size is usually 2 to 3 inches, 5 to 7.5 centimetres, or roughly 12%, – this is the normal amount of negative ease included within Woolly Wormhead knit and crochet Hat patterns.
All Woolly Wormhead patterns list both the Finished Size – i.e. the finished circumference of the Hat, and the To Fit Size – i.e. the head circumference size of the intended wearer. With this information you can decide which size is best for you if you fall between sizes, or if you prefer more or less negative ease in your Hats.
Besides negative ease, another factor that determines fit is personal choice. Some people like their Hats with little or no negative ease for a more casual look, some people prefer a tighter fitting Hat for a sportier look. This preference in fit is also affected by the style of the Hat, so do consider how the Hat will be worn in relation to the measurements given in the pattern. All Woolly Wormhead patterns include a range of sizes as well as the finished measurements to help determine which size is the best one to make. You’ll also find notes on adjustment, where applicable, to help you achieve a wider range of sizes outside of the pattern or fine tune the pattern to your size.
Typical Sizes
Below is a chart showing typical head sizes by age. The measurements given are in both metric and imperial, and cover head circumference, head length and mid-ear to mid-ear points for positioning earflaps.
Find the measurements provided in text format for each size below the chart.
These measurements were gained with the help of the Head Measuring Game and from my own experience from years of travelling to teach Hat design and hosting Hat clinics.
Diagram 2: this chart shows the typical measurements by age
Head Circumference by age in metric
Preemie: 30.5 centimetres
Newborn: 35.5 centimetres
6 months: 40.5 centimetres
12 months: 45.5 centimetres
Child, teenager or small adult: 50.5 centimetres
Average adult: 56 centimetres
Large adult: 61 centimetres
Extra large adult: 66 centimetres
Head Circumference by age in imperial
Preemie: 12 inches
Newborn: 14 inches
6 months: 16 inches
12 months: 18 inches
Child, teenager or small adult: 20 inches
Average adult: 22 inches
Large adult: 24 inches
Extra large adult: 26 inches
Head length by age in metric
Preemie: 11 centimetres
Newborn: 12.5 centimetres
6 months: 14.5 centimetres
12 months: 16.5 centimetres
Child, teenager or small adult: 18.5 centimetres
Average adult: 21 centimetres
Large adult: 23.5 centimetres
Extra large adult: 25 centimetres
Head length by age in imperial
Preemie: 4.25 inches
Newborn: 5 inches
6 months: 5.75 inches
12 months: 6.5 inches
Child, teenager or small adult: 7.25 inches
Average adult: 8.25 inches
Large adult: 9.25 inches
Extra large adult: 10 inches
Mid-ear to mid-ear across the front then back by age in metric
Preemie: 15.75 centimetres, 14.75 centimetres
Newborn: 19 centimetres, 16.5 centimetres
6 months: 22.25 centimetres, 18.25 centimetres
12 months: 24.5 centimetres, 21 centimetres
Child, teenager or small adult: 27.75 centimetres, 22.75 centimetres
Average adult: 31.75 centimetres, 24.25 centimetres
Large adult: 35 centimetres, 26 centimetres
Extra large adult: 38 centimetres, 28 centimetres
Mid-ear to mid-ear across the front then back by age in imperial
Preemie: 6.25 inches, 5.75 inches
Newborn: 7.5 inches, 6.5 inches
6 months: 8.75 inches, 7.25 inches
12 months: 9.75 inches, 8.25 inches
Child, teenager or small adult: 11 inches, 9 inches
Average adult: 12.5 inches, 9.5 inches
Large adult: 13.75 inches, 10.25 inches
Extra large adult: 15 inches, 11 inches
eta2/ this page was updated on 13th January 2023 to sizes up to a 26 inch, 66 centimetre circumference head.
That is absolutely amazing! I’ll probably have something else to say when I’ve spent some time knitting and then The Hub gets to try it on and . . . One thing confuses me: where it says "across the front then back". I think I understand "mid-ear to mid-ear", and "by age in [measurement type]". Now, you must keep in mind that a lot of things confuse me! Does this mean measure twice — once across the front and once across the ack and they should be equal? — or? I’m an inches i.e. imperial person. I use mm metric for scaling — quite handy! But if worse gets even worse I’ll deal in mm metric . . .
This means you measure twice – our ears are not centrally placed on our heads!
So the mid-ear to mid-ear measurement taken at the front, across our forehead, will be greater than the mid-ear to mid-ear measurement when taken across the back 🙂
How do I apply these measurements when knitting a Baby Bonnet for a newborn please. It’s difficult when you dont have a baby to take actual head measurements?
Follow the size a newborn given in the table 🙂 If you know the parents are larger headed, or conversely have smaller heads than average, then it’s a safe bet that the baby might be the same. But otherwise, go with the newborn size that’s listed.
One thing about babies and kids is that they always grow, so it’s better to err on the side of too big rather than too small. The first year is when we see the most head growth!
Is there a pattern for the hat?
yes! The main photo features my ‘Staggered’ Hat pattern:
https://woollywormhead.com/product/staggered-knitting-pattern
Amazing hat designs! Unfortunately I couldn’t buy the recommended wool for the TOPH hat. I purchased a similar wool, a bit thicker it seems. Cascade 220 Superwash Wave DK 200m/100g. Could you advise on how do I adjust the pattern to achieve the same size as your pattern? Would you recommend using thiner needle?
Thank you for your help
Hi there!
The best place to get help is my Ravelry or Facebook group (our new forum here isn’t quite finished yet, very soon!) but in short, yes, trying going down a needle size. It’s best to swatch for these designs as your row gauge determines fit. You can also knit more or fewer panels to get the right size – that’s something we’ve discussed a lot on the forums 🙂
Hello, I just love your hats! And this is so very informative.
I’m curious how you measure a hat after the fact though? Say you’re looking at a hat to purchase for a child, how would you measure it for an approximate age range?
hello there!
The easiest way is to lay the Hat flat, and measure across the brim, i.e. at the lowest point that will fit around the head. That’ll be the diameter of the Hat – from there multiply that by 3.14 (Pi) and you’ll get the cirumference, which is the ‘Finished Size’ of the Hat.
Once you have the actual (Finished) size of the Hat, you can then determine what head size it will fit 🙂
FYI, I think you mean 3.14 for Pi, not 4.14.
thanks for the catch – I’ve updated my comment 🙂
What a fantastic resource! This hat sizing guide is great. It’s really nice to have the imperial and metric side by side. I find the level of detail – like including the back of the head measurements – so impressive and helpful. Thank you for the high quality post! It really goes the extra mile. See you on Ravelry!
Thanks! I hope it’s helpful 🙂
This is my first time reading this, and the amount of information is amazing! But….. I have poor sight and the text is mostly too small for me to read, even though I have set my screen at 150%. I am particularly interested in Diagram 2, under “Typical sizes”. Would it be permissible to take a screen-shot, so I can blow it up, please?
Hi there,
All of the information in the sizing chart, i.e. diagram 2, is written out in larger text underneath it. This will scale proportionally as you enlarge your screen in a much better way than the image. The image isn’t high resolution, it will only get blurrier as you enlarge, hence the text version is also included 🙂
Thanks so much for sharing this information with us so generously. I have another question. How wide and tall do you think the ear flaps should be in a hat?
This is a good question, and not one I get asked often!
I aim for approximately twice the width of the ear for earflap width, although it will depend on the size and it’s proportion overall. Narrow earflaps can end up not covering the ears unless they’re very specifically places; wider earflaps allow a bit of tolerance.
In terms of depth, they don’t need to be too deep to cover the ear, and I tend to be guided by the shape of earflap I want (this can also impact width).
In short – there isn’t a specific size of earflap to aim for, it’s more about good coverage, proportion, and shape. One I recommed to look at is my Selkie pattern – it has a classic earflap shape with good coverage in all sizes without being too deep 🙂
https://woollywormhead.com/product/selkie-knitting-pattern