Method
The calculator adds or subtracts target sleep hours plus estimated sleep latency. Sleep cycles are approximated as 90 minutes.
Example
If you want to wake at 07:00, target 8 hours of sleep and usually need 15 minutes to fall asleep, the suggested bedtime is about 22:45 the previous evening.
Common mistakes
Do not treat a bedtime estimate as a diagnosis. Caffeine, alcohol, shift work, stress, light exposure and sleep disorders can all change sleep quality even when time in bed looks adequate.
Limitations
Sleep need varies. Persistent insomnia, daytime sleepiness, snoring or breathing pauses deserve clinical attention.
References
- CDC: about sleep, accessed 2026-05-17.
Last reviewed: 2026-05-17