When to Wake Up Calculator
Enter your bedtime and get wake-up times that fall at the end of a full sleep cycle, so you wake refreshed.
How it works
asleep = bedtime + fall-asleep minutes · wake = asleep + cycles × cycle length · a cycle ≈ 90 minutes
Sleep runs in repeating cycles of light, deep and REM sleep that average about 90 minutes. Waking at the end of a cycle — rather than in the middle of deep sleep — tends to feel less groggy, so the calculator adds whole cycles onto the moment you fall asleep (your bedtime plus the minutes it takes to drift off). Five cycles is roughly 7.5 hours and six is about 9 hours; both are common adult targets. Cycle length varies by person, so treat the times as a guide, not a rule.
Worked example
Bedtime 10:30 PM with 15 minutes to fall asleep means sleep begins about 10:45 PM. Six 90-minute cycles add 9 hours, giving a wake time of 7:45 AM; five cycles gives 6:15 AM.
Frequently asked questions
Why not just count 8 hours?
Eight hours can land you mid-cycle in deep sleep, which is why alarms sometimes feel brutal. Aligning to whole ~90-minute cycles aims to have you wake during lighter sleep instead.
How many cycles should I target?
Most adults do well on five to six cycles (about 7.5 to 9 hours). Fewer than four is short sleep; the table lets you compare the options against when you must be up.
Is 90 minutes exact?
It is an average. Real cycles range from roughly 70 to 120 minutes and shift through the night, so adjust the cycle length if you know yours differs.
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This calculator is for educational purposes. Double-check important results before acting on them.