Size breakdown
6 5/8 hat size in cm and inches
A US 6 5/8 fitted hat is cut for a head that measures 20 7/8 inches around — 53 cm.
US fitted
6 5/8
circumference 20 7/8 in ÷ π
Head circumference
53.0 cm
= 20 7/8
UK size
6 1/2
= US minus 1/8
EU size
53
= cm rounded
Letter size: about S. S.A head measured up to 0.3 cm from 53.0 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 5/8 sits on the hat sizes chart
This size and its neighbours, so you can compare at a glance:
| 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 |
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