A calm body of water under a full moon at night

Bedtime calculator · data from NIH, CDC and NSF

What time should you go to bed tonight?

Pick the time you have to wake up. You get three bedtimes that end on a full 90-minute cycle, so the alarm catches you in light sleep instead of the deep kind.

Counts in 90-minute cycles plus 15 minutes to fall asleep. How we calculate

Population averages · one cycle is 70–120 minutes · 194 pages · snapshot October 3, 2026

Photo by Kyle Johnson on Unsplash

Wake-up times people ask about

Each page shows the three bedtimes, the cycle timeline and what the numbers mean for a weeknight. All 96 wake-up times →

Wake at5:00 ambed by 9:15 pmWake at5:15 ambed by 9:30 pmWake at5:30 ambed by 9:45 pmWake at5:45 ambed by 10:00 pmWake at6:00 ambed by 10:15 pmWake at6:15 ambed by 10:30 pmWake at6:30 ambed by 10:45 pmWake at6:45 ambed by 11:00 pmWake at7:00 ambed by 11:15 pmWake at7:15 ambed by 11:30 pmWake at7:30 ambed by 11:45 pmWake at7:45 ambed by 12:00 amWake at8:00 ambed by 12:15 am

How much sleep do you actually need?

Two expert panels looked at the same studies and landed in nearly the same place. Bars show the recommended range for each age; the lighter bars are hours that may still be fine for some people.

  • 7–9 h for adults 18–64 (NSF 2015) — AASM says 7 or more.
  • 8–10 h for teenagers 14–17; under 7 is not recommended.
  • 7–8 h for adults 65+ — the only group whose range narrows.
Sleep needs by age →
Recommended hours of sleep per 24 h, by age
4h6h8h10h12h14h16h18h20hNewborn14–17 hInfant12–15 hToddler11–14 hPreschooler10–13 hSchool-age child9–11 hTeenager8–10 hYoung adult7–9 hAdult7–9 hOlder adult7–8 h

Sources: National Sleep Foundation panel (Hirshkowitz 2015); AASM 2015/2016 · as of October 3, 2026

Three more numbers for tonight

A person asleep under a blanket, face not visible
Photo by Annie Spratt on Unsplash

How long should a nap be?

26 min

NASA's in-flight study: a 26-minute nap improved performance 34% and alertness 54%. Past 30 minutes you risk waking groggy.

A brown ceramic cup of coffee on a table
Photo by Jakub Dziubak on Unsplash

When is the last coffee?

5 h

Caffeine's half-life is about 5 hours. Half of a 96 mg cup is still in you at 5 pm if you drank it at noon.

A window with rain drops at night
Photo by Max van den Oetelaar on Unsplash

White, pink or brown noise?

−3 dB

Pink noise drops 3 dB per octave — closer to steady rain than TV static. Here is what the studies actually found.

Caffeine left after one 96 mg cup of brewed coffee
0h2h4h6h8h10h12h964824half gone at 5 h

Half-life 5 h (IOM 2001); FDA states 4–6 h (shaded) · as of October 3, 2026

The last-coffee rule, in numbers

In the one controlled study that tested it, 400 mg of caffeine taken six hours before bed still cut total sleep by more than an hour — even when people felt fine.

If tonight's bedtime is 10:45 pm, six hours earlier is 4:45 pm, and a cup at that time leaves about 42 mg at lights out.

Caffeine cutoff by bedtime →

Guides

White vs pink vs brown noise for sleep: what the colours mean and what the research foundWhite noise is flat and hissy, pink falls 3 dB per octave like steady rain, brown falls 6 dB like distant surf… · 5 minWhy am I still tired after 7 hours of sleep?Seven hours is inside the adult range, so the usual suspects are elsewhere: waking mid-cycle, a bedtime that d… · 5 minHow to use a sleep timer with sleep sounds (and why not to play them all night)Sound helps most while you are falling asleep; later it can wake you. How long to set the timer, what volume, … · 4 minWhat time should I go to bed to wake up at 5 am?9:15 pm for five cycles, 7:45 pm for six, 10:45 pm at minimum. A 5 am alarm is an early schedule; here is how … · 5 minHow long should a power nap be? What NASA, and a 10-vs-30-minute trial, foundTen to twenty-six minutes refreshes without grogginess; thirty or more risks waking from deep sleep. The numbe… · 5 minSleep debt: is it real, and can you pay it back?Short nights add up, and the effects are measurable even when you feel fine. Weekend catch-up repays some of i… · 5 min

All guides → · How every number on this site is calculated →