How big is a brain?

The brain weighs about 3 pounds (1.36 kilograms) in women and about 3.3 pounds (1.49 kilograms) in men. (These weights are for fresh brains; a brain that has been preserved in formalin weighs more.) The brain is about 2% of a person's body weight, but it uses about 20% of the body's total energy.

For comparison, the average adult heart weighs between 10 and 12 ounces, and the average adult liver weighs between 3 and 4 pounds.