Does Head Size Increase With Age? No — Skull Growth Stops in Early Adulthood

Head circumference plateaus by age 18–20.** The brain reaches ~95% adult volume by age 6, full size by late teens. Skull sutures fuse early 20s.

What *Can* Change in Adulthood

• Soft tissue: Scalp fat, muscle atrophy/hypertrophy, edema → minor contour changes.
• Bone remodeling: Frontal bossing (acromegaly, Paget’s), calvarial thinning (aging, hyperparathyroidism).
• Posture: Forward head → apparent occipital prominence.
• Pathology: Hydrocephalus (ventriculomegaly), tumors, fibrous dysplasia — true size increase.

Measurement Nuance

• Tape over supraorbital ridges + occipital prominence.
• Adult male mean: 57–58 cm; female: 55–56 cm.
• >2 cm change in adult → investigate (mass, fluid, bone disease).

Myth Origins

• Cartilage growth (ears, nose) continues lifelong — misattributed to skull.
• Hat size “creep” from hair loss, skin laxity, measurement inconsistency.

Your hat size at 25 is your hat size at 85 — unless disease intervenes.