How much sleep you need, by age

“How much sleep do I need” has a real answer, and it depends almost entirely on your age. Newborns run on 14 to 17 hours a day. School-age children need 9 to 12. Teenagers need 8 to 10 but rarely get it, because puberty shifts the body clock about two hours later, which makes a 7 am school start feel like 5 am. Adults do best on 7 to 9 hours, and that number holds surprisingly steady from age 18 all the way to 65.

The other number worth owning is 90: the length in minutes of one full sleep cycle. Each cycle walks through light sleep, deep slow-wave sleep, and REM, where the vivid dreaming happens. REM periods stretch as the night goes on, which is why the alarm so often ambushes you mid-dream, and why cutting sleep short costs you a disproportionate amount of it.

These are exactly the facts people look up, nod at, and forget by Thursday. So this page does not just tell you; the deck below asks you, with wrong answers close enough to the truth that you have to actually know it.

Play it free, right here. Want the numbers to survive until they change your bedtime? The app re-asks each fact on the day you would otherwise lose it.