How the Calculation Works
The formula is: Bedtime = Wake time − 15 min (sleep latency) − (number of cycles × 90 min). For 5 cycles: wake time minus 7.5 hours minus 15 minutes = your bedtime. For 6 cycles: add another 90 minutes.
The 15-minute sleep latency accounts for the average time it takes a healthy adult to fall asleep after getting into bed. If you typically fall asleep faster (some people are asleep in 5 minutes), your optimal bedtime is 10 minutes later. If you take longer (20-25 minutes), it is 5-10 minutes earlier.
For the most common alarm time — 7:00 AM — the answer is 11:15 PM (5 cycles, 7.5 hours). Going to bed at "about 11" or "midnight" is close but typically results in waking mid-cycle. The 15 minutes makes a measurable difference.
What Time Should You Actually Aim For?
Beyond the calculation, consider your chronotype. Natural morning types (larks) find it easier to maintain early bedtimes. Natural evening types (owls) find that 11 PM or later bedtimes align better with when their melatonin actually rises. Using the calculator for your natural wake time — rather than your aspirational wake time — gives you the most achievable schedule.
- 1Start with your fixed wake time, not your desired bedtime. The alarm is the anchor. Everything else is calculated backwards from it.
- 2Give yourself the 15-minute buffer in the calculation. Do not try to fall asleep the instant you get into bed — allow for the transition.
- 3If your calculated bedtime feels too early, try the 4-cycle option (6 hours) on difficult nights — it is a real cycle-aligned option, just not optimal as a daily target.
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