Sleep calculator: when to go to bed for the time you wake
Adults are advised to sleep 7 hours or more a night, and 7 to 9 hours suits most people. Sleep runs in cycles of roughly 90 minutes, so waking at the end of a cycle can feel easier. Enter your wake time and this calculator lists bedtimes for five and six cycles, allowing 15 minutes to fall asleep.
- Go to bed at
- 10:45 pm
- 5 cycles · 7.5 hours of sleep
- For 9 hours
- 9:15 pm
- 6 cycles
- Shortest advised
- 11:14.700000000000045 pm
- about 7 hours
How it works
Cycles
A full cycle averages about 90 minutes but varies between 70 and 120. Treat the times as a guide, not an exact schedule.
The target
Five cycles is 7.5 hours and six is 9 hours. Consistency of wake time matters more than any one night.
Questions
How much sleep do adults need?
Seven hours or more on a regular basis, according to the American Academy of Sleep Medicine and Sleep Research Society consensus.
Is it bad to sleep more than 9 hours?
Occasionally it is normal, for example after illness or hard training. Regularly needing much more can be worth discussing with a clinician.
When should I see someone about sleep?
Loud snoring with pauses in breathing, daytime sleepiness that affects driving or work, or insomnia lasting weeks are reasons to talk to a clinician.
Related calculators
Sources
Accurate as of November 12, 2026. Training and nutrition guidance only, not medical advice. See a clinician for symptoms, injury or a medical condition.
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