The average size of an adult human brain weighs 3 pounds and is about 6 inches long. At birth, the human brain weighs only ¾ pound.
Although the average adult brain is roughly the same size in all humans, there are differences in the sizes of different areas of the brain. Researchers have found that the frontal lobes and limbic cortex of women's brains are larger than they are in men's brains. The parietal cortex and amygdala tend to be larger in men. Men, on average, have slightly larger brains than women. A male brain weighs approximately 3.5 ounces more than a female's.