Sleep Calculator
Compare sleep durations and clock times. The results do not predict sleep stages.
90 minutes × count + your fall-asleep buffer. This does not predict sleep stages. Prioritize enough total sleep, not a calculated cycle boundary.
90 minutes × count + your fall-asleep buffer. This does not predict sleep stages. Prioritize enough total sleep, not a calculated cycle boundary.
How to use
- Choose whether you know your wake-up time or bedtime.
- Enter the time.
- Adjust the fall-asleep buffer.
- Compare total sleep durations and set a device alarm if needed.
Quick reference
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| Browser limits | Sleep-cycle times are planning estimates, not medical advice or a guarantee of sleep quality. |
Questions and answers
Why 90-minute cycles?
Can I send a result to the alarm clock?
Is this medical advice?
More details and related tools
How it works
Choose a wake-up time to see suggested bedtimes, or choose a bedtime to see possible wake-up times. The calculator includes a fall-asleep buffer before the first estimated sleep cycle. Sleep needs vary; CDC recommends at least 7 hours for adults aged 18–60, and persistent sleep problems are a reason to talk with a qualified health professional.
Example calculation
With the default 15-minute fall-asleep buffer, a 7:00 wake-up time gives a 23:15 bedtime for 5 cycles: 7 hours 30 minutes of estimated sleep plus 15 minutes to fall asleep. A 6-cycle result for the same wake-up time lands at 21:45. Treat those as planning anchors, not a promise that sleep stages will line up perfectly.
If the suggested time feels unrealistic, adjust the buffer first. The tool allows 0–90 minutes because the most useful input is often not the cycle count, but how long it usually takes you to fall asleep on that kind of night.
Helpful next step
If you want a fuller wind-down flow after choosing a time, a bedtime planner and sleep timer can help plan the routine around the clock time.
Related tools
Further reading
Sources checked
Source and scope review: 5 September 2026. Automated editorial review by Codex; not a medical, coaching or kitchen test. Each source supports the limited statement next to it.
- Sleep cycles repeat roughly every 80–100 minutes; this calculator does not measure sleep stages. nhlbi.nih.gov
- CDC recommends at least seven hours for adults aged 18–60; recommendations differ by age. cdc.gov