Look, REALLY Have to Study For This Final. I Don't Need THAT Much Sleep, Do I? Well, that depends. If you're a newborn baby, (who makes it a point to study for finals) you need 17 to 18 hours, 50% of which you'll spend in REM sleep. In five years (when exams will be much easier now that you're walking and talking), you'll only need 10 to 12 hours, only 20% of which you'll spend in REM. The average young adult needs only about 8 hours of sleep, though some need less and some need more. The elderly spend even less time asleep, but their sleep is very easily interrupted.
Stages of Sleep
Patterns of Sleep