What percentage of an average human's life is spent sleeping?

According to Phys.org, an average person sleeps for one-third of his life. Because of sleep, about 318 months in an average person’s life is spent lying in bed, based on the average life expectancy of 79.5 years, according to The Fact Site.

According to Psych Central, the optimal amount of sleep varies from person to person. The standard recommendation of eight hours for sleep is a myth. To know how long an individual must sleep, that person must allow himself to sleep for as long as needed. Doing this creates a pattern of falling asleep and waking up at the same time.