How much sleep do adults actually need, and is six hours enough?

Seven to nine hours is the range for most adults, and the proportion who genuinely function well on six is very small — far smaller than the proportion who believe they do. The catch is that chronic sleep restriction impairs performance while reducing your ability to notice the impairment, so self-assessment is unreliable. A practical test: if you sleep substantially longer on holidays without an alarm, you are carrying sleep debt. Quality matters alongside duration — fragmented eight hours is not equivalent to solid seven — but most people's problem is simply not allowing enough time.