My head = 23”
Hat = about 18”?

Fits perfectly, did the pattern rows 6 times before decreasing.

In the photo, I had only done 5 repeats (I was excited to be done) and decided it was too short, so I undid the decrease, did one more repeat before doing the decrease. Length is MUCH better.

The decrease starts cabling every other row instead of every 4 rows. This seems to make the hat “pull up” and not sit snugly on the head. I might undo the decrease (again) and make the cable every 4 rows instead…fewer cable crosses but same decrease pattern.