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What time should I wake up if I go to bed at 6:45 pm?

Updated October 3, 2026 · Method: 15 min to fall asleep + 90-minute cycles · Sources: NINDS, AASM, NSF

Short answer

2:30 am

after 5 full cycles — 7 h 30 min of sleep, inside the 7–9 h most adults need.

Later, 6 cycles4:00 am9 h
Earliest, 4 cycles1:00 am6 h — short for most adults

General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.

Going to bed at 6:45 pm is early for an adult, which is exactly why it pays off: five full cycles end at 2:30 am, six at 4:00 am, both well before most alarms.

Your night from lights out at 6:45 pm to the 2:30 am alarm
12345Lights out 6:45 pmWake 2:30 am15 min to fall asleep5 cycles × 90 min = 7 h 30 min

One cycle ≈ 90 min (range 70–120) · NINDS · as of October 3, 2026

Why these alarm times

2:30 am is five cycles and 7 h 30 min; 4:00 am is six and 9 h. If the morning allows the later one, the extra cycle is mostly REM, the stage that gets squeezed on short nights. 1:00 am is the four-cycle minimum (6 h), below the 7-hour line the AASM and Sleep Research Society set for adults.

Waking at the end of a cycle usually means waking from light sleep or REM rather than deep sleep, which is why an alarm that lands here feels gentler than one that lands twenty minutes earlier. Cycles vary from 70 to 120 minutes, so each time is the centre of a window.

Here is the shape of the night. You settle at 6:45 pm and are asleep by 7:00 pm; the first and deepest slow-wave stretch arrives near 7:20 pm; by 10:45 pm you are halfway through; from about 1:55 am the final REM period runs up to the 2:30 am alarm. Cut the night short and that last REM block is what goes.

All alarm times for a 6:45 pm bedtime

AlarmCyclesSleepAdult range
1:00 am46 hbelow 7 h
2:30 am57 h 30 minwithin 7–9 h
4:00 am69 hwithin 7–9 h
5:30 am710 h 30 minabove 9 h

Formula: alarm = bedtime + 15 min + (cycles × 90 min) · methodology

Try a different bedtime

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

Related pages

Bed at 6:15 pmwake at 2:00 amBed at 6:30 pmwake at 2:15 amBed at 7:00 pmwake at 2:45 amBed at 7:15 pmwake at 3:00 am Need to wake at 2:30 am? Start from the alarmbed by 6:45 pm What the sixth cycle adds9 h

Sources

  1. Brain Basics: Understanding Sleep — National Institute of Neurological Disorders and Stroke (NIH)
  2. How Sleep Works - Sleep Phases and Stages — National Heart, Lung, and Blood Institute (NIH)
  3. Sleep cycles - Sleep Education — American Academy of Sleep Medicine
  4. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the AASM and Sleep Research Society — Sleep 38(6):843-844, 2015
  5. Sleep inertia — Sleep Medicine Reviews 4(4):341-353, 2000 (Tassi P., Muzet A.)

General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.