The Human Brain Weighing roughly three pounds, the human brain is about the size of a small cauliflower and has the consistency of tofu. Although your brain makes up only about 2 percent of your total body weight, it uses some 20 percent of the oxygen your body needs while at rest (Magistretti, 2009). The oxygen is used in breaking down glucose to supply the brain with energy.
Geoff Tompkinson/Science Source.