Clinton -

US hat sizes are commonly in inches - by the diameter of the (round) post it fits on. I have found that ordering by mail is not reliable, due to size tolerance as well as to quality. Apparently some makers use a "fuzzy post" to measure, as there's quite a lot of variation in hats all marked as the same size, even when dealing with the rare real hat dealer or maker.

Assuming an accurate measure, a 7-1/2 would be a a bit large to be comfortable on my little pin-head, and at the rate I'm losing the hair the head may be smaller than my existing hats were originally built. With sufficient wear a good hat will "shrink in place" a bit, but there are limits to how far one can go.

One of my first "real" hats felt fairly comfortable, until I noticed that the tops of my ears were getting "chapped" from it resting on them. (Actually, one ear or the other, depending on the degree of jaunty tilt. I'm a bit less jaunty now, perhaps; but a proper sizing is needed.)

John