Sleep Calculator
90-minute REM cycle bedtimes and wake times — wake at the end of a cycle, not in the middle of one.
Result
- Sleep latency assumed14 min (typical adult)
- Adult target7-9 hours (5-6 cycles)
The average person takes 14 minutes to fall asleep — this calculator adds that offset.
To wake up refreshed at 7:00 AM, sleep at one of these times:
Waking at the end of a 90-minute cycle (lighter sleep) feels less groggy than waking mid-cycle. A good night is 5-6 complete cycles.
How to use this calculator
- If your alarm is fixed, use "Wake at" mode and pick the bedtime that fits your real schedule.
- If you control bedtime, use "Sleep at" mode to find an alarm-friendly wake time.
- Don't obsess over hitting the exact minute — ±15 min is fine; your cycle isn't metronomic.
- Consistency matters more than perfection. Same bed and wake time daily beats a random schedule.
About this tool
Sleep happens in roughly 90-minute cycles that move from light NREM down to deep slow-wave sleep and back up through REM. Waking at the end of a cycle (lighter sleep) feels much less groggy than waking mid-cycle. This calculator picks bedtimes or wake times that align with whole cycles, plus 14 minutes for the average time it takes to actually fall asleep. The 90-minute number is the population average — your real cycle length is anywhere from 70 to 110 minutes, so treat the suggested times as ±15 minute targets, not stopwatches. Most adults need 5–6 cycles (7.5–9 hours) for consistent good function.
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