Calculator
Sleep Cycle Alarm Calculator
Timezone (Global)
Calculates optimal times based on 90-minute sleep cycles (5-6 cycles) plus 15 minutes to fall asleep.
Current Time in Selected Zone
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Recommended Sleep Times
Bedtime -> Wake-up Time
Input time is based on the selected timezone.
Automatically includes 15 minutes to fall asleep.
5 Cycles
06:45
+1 day
6 Cycles
08:15
+1 day
Wake-up Time -> Bedtime
Calculates backward from your alarm time.
Based on 5-6 cycles (90 minutes each) + 15 minutes to fall asleep.
5 Cycles
23:15
-1 day
6 Cycles
21:45
-1 day
Frequently Asked Questions
What is a sleep cycle?
A sleep cycle lasts approximately 90 minutes and consists of light sleep (N1/N2), deep sleep (N3/slow-wave), and REM sleep. A full night typically includes 4–6 complete cycles. Waking mid-cycle — especially during deep sleep — causes grogginess (sleep inertia).
Why does waking at the right cycle time help?
Waking at the end of a cycle (during light sleep) feels more natural and refreshing. Waking during deep sleep disrupts restoration processes and causes prolonged grogginess. This tool calculates alarm times aligned with cycle endpoints for a given bedtime or desired wake time.
Should I use this to decide my bedtime?
It is a helpful guide, not a rigid rule. Individual cycle lengths vary (80–110 minutes). Using these times consistently can improve sleep quality, but total sleep duration matters most — most adults need 7–9 hours (4.7–6 full cycles).