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Sleep Calculator

Best bedtime and wake-up time by sleep cycles.

I want to

Try to fall asleep at one of these times:

  • 9:16 PM

    6 cycles · 9 h sleep · best

  • 10:46 PM

    5 cycles · 7.5 h sleep · best

  • 12:16 AM

    4 cycles · 6 h sleep

  • 1:46 AM

    3 cycles · 4.5 h sleep

Sleep comes in cycles of about 90 minutes. Waking at the end of a cycle, instead of in the middle, helps you feel fresh. Times include about 14 minutes to fall asleep. Adults need 7–9 hours; teens 8–10.

How to use

  1. 1Choose wake-up time, bedtime or sleep now.
  2. 2Enter the time.
  3. 3Pick one of the suggested times; 5 or 6 cycles is best.
  4. 4Set your alarm or head to bed on time.

Frequently asked questions

Why 90-minute cycles?

Sleep moves through light, deep and REM stages in cycles of about 90 minutes. Waking between cycles feels much easier than waking from deep sleep.

How much sleep do I need?

Most adults need 7–9 hours (5–6 cycles). Teenagers need 8–10 hours and school children 9–12.

Why add 14 minutes?

That's roughly how long an average person takes to fall asleep after lying down.

Is this medical advice?

No. Cycles vary from person to person. See a doctor if you regularly can't sleep or feel tired all day.

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