What percentage of his brain did Einstein use?

Einstein used 100 percent of his brain just as all people do. The contention that humans use only about 10 percent of their total brain capacity is a myth that is sometimes attributed to Einstein.

The brain, though the hub of the human body, is still somewhat of a mystery to scientists. It is believed that the 10 percent myth may have evolved from the misunderstanding that scientists understand only about 10 percent of how and why the brain functions. Much of the brain's tissue and cells seems to serve no other function than to support the neurons in the brain, which account for only about 10 percent of the brain's total makeup.