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Sleep calculator: bedtime, wake time and sleep debt

Short answer

Adults should sleep 7 or more hours a night on a regular basis, according to the American Academy of Sleep Medicine and Sleep Research Society. To wake at 7:00 AM after 7 hours of sleep, allowing 15 minutes to fall asleep, go to bed by 11:45 PM. The calculator below also plans around 90-minute blocks and adds up your sleep debt.

Last reviewed 12 October 20263 published sourcesNot medical advice

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Bedtime and wake-time calculator

Plans around the 7-hour minimum and 90-minute blocks. Real sleep cycles vary, so treat the blocks as a rough guide.

Plan from
min

Adjust to what is typical for you.

Go to bed at one of these times:

  • 9:45 PM

    Bed for 9 h of sleep · 6 × 90-minute blocks

  • 11:15 PM

    Bed for 7 h 30 min of sleep · 5 × 90-minute blocks

  • 11:45 PM

    Bed for 7 h of sleep · the 7-hour minimum

Sleep debt calculator

Enter the hours you actually slept on each of the last seven nights, for example from the Sleep section of the Health app.

h
h
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Net sleep debt

30 min

against 7 h a night

Average per night

6.9 h

Nights under 7 h

3 of 7

Across 7 nights you slept 48.5 h. Your short nights added up to 2 h 30 min below target. The AASM/SRS consensus recommends 7 or more hours on a regular basis; 3 of these nights fell short of that.

What time should I go to bed?

The American Academy of Sleep Medicine and Sleep Research Society recommend that adults sleep 7 or more hours per night on a regular basis (Watson et al., 2015 (AASM/SRS)). The table works back from common alarm times, allowing 15 minutes to fall asleep.

Bedtimes for common wake-up times (15 minutes to fall asleep)
Wake at7 h sleep7 h 30 min (5 blocks)9 h (6 blocks)
5:00 AM9:45 PM9:15 PM7:45 PM
5:30 AM10:15 PM9:45 PM8:15 PM
6:00 AM10:45 PM10:15 PM8:45 PM
6:30 AM11:15 PM10:45 PM9:15 PM
7:00 AM11:45 PM11:15 PM9:45 PM
7:30 AM12:15 AM11:45 PM10:15 PM
8:00 AM12:45 AM12:15 AM10:45 PM

About 90-minute sleep cycles

Through the night you move through non-REM and REM sleep several times, and REM sleep first appears about 90 minutes after falling asleep (NINDS). That is why many sleep calculators count in 90-minute blocks. Real cycles vary between people and across the night, so a block-based wake time is a rough aid, not a guarantee you will wake between cycles. Getting enough total sleep matters more than landing on an exact block.

How sleep debt adds up

Sleep debt is the gap between the sleep you need and the sleep you get, added up over several nights. In a lab study, people limited to 6 hours a night for two weeks built up thinking and reaction-time deficits equivalent to up to two nights without any sleep, while their own sleepiness ratings rose only a little after the first few days (Van Dongen et al., 2003). The consensus statement notes that sleeping more than 9 hours regularly may be appropriate for people recovering from sleep debt (Watson et al., 2015 (AASM/SRS)).

Caffeine late in the day can shorten sleep too: check your cutoff with the caffeine calculator.

Skip the typing: your watch already knows

Reps reads the sleep your Apple Watch already records and weighs it into the same daily readiness as your resting heart rate and recent training strain.

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Common questions

How many hours of sleep do adults need?

The AASM and Sleep Research Society consensus says adults should sleep 7 or more hours per night on a regular basis. Sleeping more than 9 hours regularly may be appropriate for young adults, people recovering from sleep debt and people with illnesses.

Are sleep cycles really 90 minutes?

Roughly. REM sleep first appears about 90 minutes after falling asleep and the night repeats several non-REM and REM cycles, but cycle length varies from person to person and through the night. Use 90-minute blocks as a planning aid, not a precise schedule.

Can you catch up on sleep debt?

Extra sleep helps, but debt adds up faster than it feels. In Van Dongen et al.'s 2003 lab study, two weeks of 6-hour nights produced thinking deficits equivalent to up to two nights without sleep, while people's own sleepiness ratings rose only a little after the first few days.

Sources

Figures on this page were checked against these publications on 12 October 2026.

  1. Watson NF, Badr MS, Belenky G, Bliwise DL, Buxton OM, Buysse D, et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. 2015;38(6):843–844. doi.org/10.5665/sleep.4716
  2. National Institute of Neurological Disorders and Stroke. Brain Basics: Understanding Sleep (last reviewed 25 February 2025). www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-understanding-sleep
  3. Van Dongen HPA, Maislin G, Mullington JM, Dinges DF. The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep. 2003;26(2):117–126. doi.org/10.1093/sleep/26.2.117

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