Size breakdown

6 3/4 hat size in cm and inches

If your tape reads close to 53.9 cm (21 1/4 in), US 6 3/4 is the fitted size to look for.

US fitted

6 3/4

circumference 21 1/4 in ÷ π

Head circumference

53.9 cm

= 21 1/4

UK size

6 5/8

= US minus 1/8

EU size

= cm rounded

Letter size: about S. S.A head measured up to 0.3 cm from 53.9 cm matches this size; between sizes, take the next size up for a non-adjustable hat.Letter sizes vary by brand; check the brand's own chart.

Where 6 3/4 sits on the hat sizes chart

This size and its neighbours, so you can compare at a glance:

Hat size chart: US, UK and EU hat sizes with head circumference in centimetres and inches
US	UK	Head (cm)	Head (inches)	EU	Letter
6 5/8 hat size	6 1/2	53.0	20 7/8	53	S
6 3/4 hat size	6 5/8	53.9	21 1/4	54	S
6 7/8 hat size	6 3/4	54.9	21 5/8	55	S

Scroll sideways inside the table on small screens if you do not see every column. Letter sizes vary by brand; check the brand's own chart.

Next to 6 3/4: US 6 5/8 Next to 6 3/4: US 6 7/8 What size hat is 54 cm?

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