Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles.
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Result
Optimal times
Sleep occurs in 90-minute cycles of light sleep, deep sleep, and REM. Waking at the end of a cycle leaves you feeling more refreshed than waking mid-cycle. Adults typically need 5–6 cycles (7.5–9 hours). The calculator adds an average 14-minute sleep-onset latency.
Frequently asked questions
How many hours of sleep do adults need?
Most adults need 7–9 hours. Less than 6 hours consistently is associated with increased health risks.
What are sleep cycles?
Each sleep cycle lasts about 90 minutes and progresses through light sleep, deep sleep, and REM. Waking at the end of a cycle feels most natural.