Measure the head at the widest part, usually just above your ears and across the mid forehead. Use a measuring tape or ribbon that DOES NOT STRETCH (don't use a string). Keep the tape level and firm. Meaure three times and take an average. Measure to the last 1/8" or 0.1 cm, choose a size range and include the actual measurement with your order.
Some individuals know their hat size, say 7-1/4. However since there are two or more sizing schemes for hats, the actual measurement can vary by up to 3/4". So always measure.
Xsmall 18" to 20" (47.8 - 50.8 cm)
Small 20" to 21" (50.8 - 53.3 cm)
Medium 21" to 22" (53.3 - 55.9 cm)
Large 23" to 24" (58.4 - 61 cm)
XL 24" to 25" (61 - 63.5 cm)
XXL 25" to 26" (63.5 - 66 cm)
Small 21-1/2" to 22-1/4" (sizes 6-3/4 to 7)
Medium 22-1/2" to 23" (sizes 7-1/8 to 7-1/4)
Large 23-3/8" to 23-1/2" (sizes 7-3/8 to 7-1/4)
XL 24" to 24-1/2" (sizes 7-5/8 to 7-3/4)
XXL 25" (size 7-7/8); oversize is 25-1/4" or size 8. Larger sizes just ask.
For larger sizes, the dome size can be adjusted proportionally. Let me know your dome size by adding this measurement. Measure from the mid forehead up over the top and down the back to that divot just below the skull. Women's average is about 13" while men's average is 14".
Tip: Roughly, head circumference equals Pi x hat size, or 3.14 times the hat size, give or take, since the equations for measuring the circumference of a circle, oval- and egg-shapes are slightly different.
For a hat worn snugly, such as a fedora or cadet hat, I will subtract 1/4"; for a trapper bomber hat, I'll add 1" to the finished item.
Most heads are oval shaped and accounts for 80% of us. The remaining 20% have round or elongated-oval heads.
For the same circumference, a hat will feel tight on the sides of a round head and tight in the front or back on an elongated-oval head.
If you notice that your hats fit uncomfortably for a size that should otherwise fit, find out what shape your head is by bowing forward and asking a friend to tell you. Knowing that, I can recommend certain styles or modify an existing style to fit better.
Generally, for example, bowlers and newsboys favor round heads and fedoras and flat caps favor elongated heads, but I can modify the shape.
Generally weight loss doesn't affect hat size unless one has a fleshy head. However men's head sizes tend to be the greatest between ages 35 and 55, so a hat that fit well at 25 may not at 35.
Short hair or no hair does affect the hat size. Going from a full head of hair to no hair may reduce the hat size by about 1/2 inch, more, if the hair was curly. When fitting a fedora, measure for the type of hair it will be worn over.
For other tips, see www.cherrypat.com/blogs/news