A Guide to Hat Sizing
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.
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.