Head circumference to hat size

Your hat size comes straight from your head circumference. Type the measurement to convert it.

Hat size calculator

Your head circumference

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Enter your head measurement to see your size in every system.

European sizes: the hat size is the circumference in cm. 57 cm is a size 57.
US sizes: divide the circumference in inches by 3.1416 and round to the nearest eighth. 22.5 in is a 7 ⅛.
UK sizes: one eighth smaller than US sizes.
Letter sizes: check the brand chart. M is usually 56 to 57 cm (7 to 7 ⅛).

Head circumference to hat size chart
cm	Inches	US	UK	Letter
46	18 ⅛	5 ¾	5 ⅝	–
47	18 ½	5 ⅞	5 ¾	–
48	18 ⅞	6	5 ⅞	–
49	19 ¼	6 ⅛	6	–
50	19 ⅝	6 ¼	6 ⅛	–
51	20 ⅛	6 ⅜	6 ¼	–
52	20 ½	6 ½	6 ⅜	XS
53	20 ⅞	6 ⅝	6 ½	XS
54	21 ¼	6 ¾	6 ⅝	S
55	21 ⅝	6 ⅞	6 ¾	S
56	22	7	6 ⅞	M
57	22 ½	7 ⅛	7	M
58	22 ⅞	7 ¼	7 ⅛	L
59	23 ¼	7 ⅜	7 ¼	L
60	23 ⅝	7 ½	7 ⅜	XL
61	24	7 ⅝	7 ½	XL
62	24 ⅜	7 ¾	7 ⅝	XXL
63	24 ¾	7 ⅞	7 ¾	XXL
64	25 ¼	8	7 ⅞	3XL
65	25 ⅝	8 ⅛	8	3XL
66	26	8 ¼	8 ⅛	3XL

1 Use a soft tape measure, or a string and a ruler.
2 Wrap it around your head where the hat will sit: about 1 cm (⅜ in) above your ears and across the middle of your forehead.
3 Keep the tape level and snug, not tight. Do not pull it in.
4 Read the number where the tape overlaps. Measure two or three times and use the largest value.
5 Type the number into the calculator, or find it in the chart.

What hat size is a 57 cm head circumference?

US 7 ⅛, UK 7, EU 57, usually a Medium.

What hat size is a 22 inch head?

A fitted 7, which is 56 cm.

Should I round up or down?

Round up for fitted caps and felt hats, and down for stretch-fit caps and beanies.