Human Brain Size: Average Weight & Dimensions

The average adult human brain weighs 1.3–1.4 kg (∼3 lbs) and measures approximately 15 cm (6 in) long, 14 cm wide, 9 cm high. Volume: ∼1,200–1,300 cm³.

Variability

Size varies by sex (male brains ~10% larger on average, proportional to body size), age (peaks early 20s, gradual decline), and individual genetics. Brain size does not correlate with intelligence. Cognitive ability depends on neuronal density, synaptic connectivity, cortical folding, and network efficiency—not volume.

Key Structures

• Cerebrum (85% of weight): higher functions
• Cerebellum (10%): coordination, balance
• Brainstem: vital autonomic control

Neuroimaging (MRI) provides precise individual measurements for clinical/research purposes.