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Sleep Cycle Calculator

Find the best time to go to bed or wake up refreshed.

I want to

To wake up refreshed at 7:00 AM, go to bed at one of these times:

  • 9:45 PM6 cycles · 9 hours sleepRecommended
  • 11:15 PM5 cycles · 7.5 hours sleepRecommended
  • 12:45 AM4 cycles · 6 hours sleep
  • 2:15 AM3 cycles · 4.5 hours sleep

Each sleep cycle lasts about 90 minutes. Waking at the end of a cycle, rather than in the middle of deep sleep, helps you feel less groggy. Most adults need 7 to 9 hours (5 to 6 cycles).

Results are estimates for general information only and are not medical advice. Talk to a doctor or other qualified health professional about your health. Read our disclaimer.

When to use it

Use this calculator to choose a bedtime or alarm time that lets you wake at the end of a sleep cycle. Many people feel less groggy when they wake between cycles instead of in the middle of deep sleep. It is handy before an early start, a flight, an exam or any day you want to feel fresh.

How to use it

  1. Under I want to, choose one option:
    • Wake up at to get bedtimes for a set alarm time.
    • Go to bed at to get wake-up times for a planned bedtime.
    • Sleep now to get wake-up times if you go to bed right away.
  2. Enter the time, unless you chose Sleep now.
  3. Choose the Time it takes you to fall asleep: about 5, 15 or 30 minutes.
  4. Read the list of times. Each one shows the number of cycles and hours of sleep, and the 5 and 6 cycle options are marked Recommended.

Worked example

You need to wake up at 7:00 AM and usually fall asleep in about 15 minutes. The calculator suggests going to bed at 9:45 PM for 6 cycles (9 hours) or 11:15 PM for 5 cycles (7.5 hours). If you have a late night, 12:45 AM gives 4 cycles, or 6 hours.

Now say you go to bed at 11:00 PM. Choose Go to bed at and enter 11:00 PM. The best alarm times are 6:45 AM for 5 cycles or 8:15 AM for 6 cycles. Setting an alarm for 7:30 AM instead might wake you in deep sleep, even though it gives you more time in bed.

Tips

  • Keep a steady routine. Going to bed and waking at the same time each day, even at weekends, helps your body clock.
  • Be honest about falling asleep. If you usually scroll on your phone for half an hour, choose 30 minutes.
  • Adjust from experience. If the suggested time still feels hard, move your alarm by 10 to 15 minutes and see what works.
  • Wind down first. Dim lights and less screen time in the last hour make it easier to fall asleep on time.

Common mistakes

  • Counting time in bed as sleep. The cycles only start once you are asleep.
  • Choosing short sleep every night. Waking between cycles helps, but it does not replace getting enough sleep.
  • Using snooze. Snoozing can drop you back into a new cycle and leave you groggier.

If you often feel tired despite enough sleep, or snore loudly, talk to a doctor.

Frequently asked questions

Why does the calculator use 90-minute cycles?

Sleep moves through light, deep and dream (REM) stages in cycles that last about 90 minutes on average. Waking at the end of a cycle, when sleep is lighter, usually feels easier than waking from deep sleep.

What if my cycles are not exactly 90 minutes?

They vary from about 70 to 120 minutes between people and through the night. Treat the times as a good starting point. If you wake groggy, try moving your alarm 10 to 15 minutes earlier or later.

How much sleep do I need?

Most adults need 7 to 9 hours, which is about five or six cycles. Teenagers and children need more. That is why the 5 and 6 cycle times are marked as recommended.

Why does it ask how long I take to fall asleep?

The cycles start once you are asleep, not when you get into bed. Adding the time it takes you to drop off makes the suggested times more accurate.

Is it bad to get only 4 cycles?

Six hours now and then is not a problem for most people, but regularly sleeping that little can affect mood, focus and health over time. Use the shorter options only when you have to.

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