How many neurons are in the brain?

There are about 86 billion neurons in the human brain, states About.com. Many sources report 100 billion neurons in the brain, but Brazilian researcher Dr. Suzana Herculano-Houzel did a study that counted the nuclei of neurons to arrive at this value.

Human and primate brains are quite comparable, though humans have many more brain cells that use up to 25 percent of the body's energy, according to About.com. Chimpanzees have about 7 billion neurons, or 1/12 the number of a human. Elephants have 23 billion neurons in their brains, or just over one-fourth the number of neurons a human has.