Question: what is the average head size in inches?
Answer: According to Wikipedia, one study in the United States shows, the average adult head circumference to be 55cm (21 3⁄4 ) in females and 57cm (22 1⁄2 in) in males. Another study conducted in UK shows a slightly different result: with the average female head size being 55.2 cm and the average male head size being 57.2 cm.