Newborn: Head Circumference - 13 inches / Top of crown to bottom of ear - 4.5-5.5 inches
2 weeks to 3 months: Head Circumference - 14 inches / Top of crown to bottom of ear - 5.5-6 inches
3-6 months: Head Circumference - 15 inches / Top of crown to bottom of ear - 6-6.25 inches
6-9 months: Head Circumference - 16 inches / Top of crown to bottom of ear - 6.25-6.5 inches
9-12 months: Head Circumference - 16.5 inches / Top of crown to bottom of ear - 6.5 inches
12-18 months: Head Circumference - 17 inches / Top of crown to bottom of ear - 6.75 inches
18-24 months: Head Circumference - 18 inches / Top of crown to bottom of ear - 7.25 inches
2-5 years: Head Circumference - 18-19 inches / Top of crown to bottom of ear -7.25-7.5 inches
Child: Head Circumference - 19-20 inches / Top of crown to bottom of ear - 7.75-8 inches
Teen: Head Circumference - 20-21 inches / Hat Height (Top of Crown to Bottom of Ear) - 8 - 8.5 inches
Adult Female: Head Circumference - 22 inches / Hat Height (Top of Crown to Bottom of Ear) - 8.75 - 9 inches
Adult Male: Head Circumference - 23 inches / Hat Height (Top of Crown to Bottom of Ear) - 9.25 - 9.5 inches