TimeZonesHoursSleepQuiz

Sleep Calculator

Hours slept, and bedtimes that fit your sleep cycles

How long did I sleep?

7.5 hours — within the 7–9 hours most adults need

Sleep cycle planner

Go to bed at one of these times:

  • 6 cycles · 9hRecommended
  • 5 cycles · 7h 30mRecommended
  • 4 cycles · 6h
  • 3 cycles · 4h 30m

What time should I go to bed?

Bedtimes that end on a full 90-minute cycle, including about 15 minutes to fall asleep.

  • Waking at 5:00 AM? Go to bed at 7:45 PM (6 cycles, 9 hours of sleep) or 9:15 PM (5 cycles, 7.5 hours).
  • Waking at 5:30 AM? Go to bed at 8:15 PM (6 cycles, 9 hours of sleep) or 9:45 PM (5 cycles, 7.5 hours).
  • Waking at 6:00 AM? Go to bed at 8:45 PM (6 cycles, 9 hours of sleep) or 10:15 PM (5 cycles, 7.5 hours).
  • Waking at 6:30 AM? Go to bed at 9:15 PM (6 cycles, 9 hours of sleep) or 10:45 PM (5 cycles, 7.5 hours).
  • Waking at 7:00 AM? Go to bed at 9:45 PM (6 cycles, 9 hours of sleep) or 11:15 PM (5 cycles, 7.5 hours).
  • Waking at 7:30 AM? Go to bed at 10:15 PM (6 cycles, 9 hours of sleep) or 11:45 PM (5 cycles, 7.5 hours).
  • Waking at 8:00 AM? Go to bed at 10:45 PM (6 cycles, 9 hours of sleep) or 12:15 AM (5 cycles, 7.5 hours).

Hours slept on common nights

  • 10:00 PM to 6:00 AM is 8 hours of sleep.
  • 11:00 PM to 7:00 AM is 8 hours of sleep.
  • 11:30 PM to 6:30 AM is 7 hours of sleep.
  • 12:00 AM to 7:30 AM is 7 hours 30 minutes of sleep (7.5 hours).
  • 1:00 AM to 6:00 AM is 5 hours of sleep — below the 7–9 hours most adults need.
  • 2:00 AM to 9:00 AM is 7 hours of sleep.

How the sleep cycle math works

Sleep isn't one continuous state — it runs in cycles of light sleep, deep sleep, and REM that average roughly 90 minutes each. Waking at a cycle boundary usually feels easier than being pulled out of deep sleep mid-cycle, even with slightly less total sleep. The planner works backward from your wake-up time in 90-minute steps and adds about 15 minutes for falling asleep.

Worked example: waking at 6:30 AM with six cycles means 6 × 90 + 15 = 555 minutes — bed at 9:15 PM.

Frequently asked questions

How many hours of sleep did I get?

Enter the time you went to bed and the time you woke up — the calculator handles overnight automatically, so 11:00 PM to 6:30 AM correctly reads 7 hours 30 minutes, shown in hours-and-minutes and decimal form.

What is a sleep cycle?

Sleep moves through light, deep, and REM stages in cycles averaging roughly 90 minutes. That is why the planner suggests bedtimes in 90-minute steps rather than round hours.

What time should I go to bed if I wake at 6:30 AM?

For six full cycles (about 9 hours of sleep) go to bed around 9:15 PM; for five cycles (7.5 hours) around 10:45 PM. Both include roughly 15 minutes to fall asleep. The planner computes this for any wake-up time.

How much sleep do adults need?

Major sleep-health bodies recommend 7–9 hours per night for most adults, with individual needs varying. The calculator flags whether your night fell inside or outside that range.

Is this medical advice?

No — cycle lengths and sleep-need ranges are population averages, and your own rhythm may differ. If you have ongoing sleep problems, talk to a doctor or sleep specialist.

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