34 · Calculators

Sleep Calculator

Pick a wake-up time to see when to go to bed, or a bedtime to see when to set your alarm, so you wake between sleep cycles.

I want to

Best bedtime

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How to use the sleep calculator

  1. Choose whether you know your wake-up time or your bedtime.
  2. Enter the time.
  3. Adjust how long it usually takes you to fall asleep.

Why 90 minutes?

Sleep runs in cycles of roughly 90 minutes, moving through light, deep and REM sleep. Waking at the end of a cycle, rather than in deep sleep, tends to feel less groggy. Most adults need five or six cycles: 7½ to 9 hours.

Cycles vary

Cycle length differs from person to person and through the night, so treat the times as a guide. A regular schedule matters more than hitting an exact minute.

Examples

Wake up at 7:00 AM, 15 minutes to fall asleep

Bed at 11:15 PM (5 cycles) or 9:45 PM (6 cycles)

Go to bed at 11:00 PM

Wake at 6:45 AM (5 cycles)

Questions

How much sleep do adults need?

Most adults need 7–9 hours a night. Teenagers and children need more.

Why add time to fall asleep?

Most people take 10–20 minutes to drift off. Adding it means the cycles start from when you actually fall asleep.

Does it use my time zone?

It only works with the clock time you enter, so it works anywhere.