How much does a human brain weigh?

The adult male human brain typically weighs between 1,300 grams and 1,400 grams (2.87 to 3.08 pounds), making up roughly 2 percent of total body mass. Adult female brains weigh 100 to 150 grams (0.22 to 0.33 pounds) less than adult male brains. Brain weight varies by age, sex, and individual physiology. Men tend to have a slightly larger and heavier brain than women have, although this difference does not correlate with intelligence. Based on autopsy reports of more than 8,000 patients with no known brain disorders, in 1994 researchers from Switzerland determined that the brain of an average adult female weighs about 1,200 grams (2.64 pounds). That is roughly the weight of an average cantaloupe. The brain of an average adult male, on the other hand, weighs about 1,340 grams (2.95 pounds). The heaviest human brain on record belonged to an unnamed epileptic patient in the Netherlands: An autopsy in 1899 found that his brain weighed 2,850 grams (6.28 pounds). Brain mass reaches its peak in young adulthood and, in most cases, gradually declines with age because of natural atrophy.

Humans do not have the heaviest brain among mammals. That distinction goes to the sperm whale (Physeter macrocephalus); the brain of this marine giant weighs about 7,800 grams (17.2 pounds). However, despite constituting only about 2 percent of body mass, the human brain is proportionally heavier than that of most other mammals. Maintaining such a massive organ requires considerable energy investment: About 20 percent of the body’s oxygen supply and blood flow are used by the human brain.