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Sleep Calculator

Optimize your rest using natural 90-minute sleep cycles. Determine when to fall asleep, wake up, or take refreshing power naps.

Typically takes about 10-20 minutes

How the Sleep Calculator Works

This calculator helps you determine the best times to go to bed or wake up by planning your sleep around 90-minute sleep cycles. Waking up at the end of a sleep cycle leaves you feeling refreshed and alert, whereas waking up mid-cycle can cause grogginess and sleep inertia.

Formula Used

Wake Time = Sleep Time + (n × 90 minutes) + 15 minutes Bedtime = Wake Time − (n × 90 minutes) − 15 minutes
n
— the number of completed sleep cycles (typically 5 or 6 cycles is optimal, equivalent to 7.5 or 9 hours of sleep)
90 minutes
— the average length of a human sleep cycle, spanning light sleep, deep sleep, and REM sleep states
15 minutes
— the average latency period (time it takes to fall asleep) added to the calculation

Example Calculation

If you need to wake up at 7:00 AM, the calculator computes Bedtime options by subtracting sleep cycles. For 6 sleep cycles (9 hours of sleep) plus 15 minutes to fall asleep: 7:00 AM − 9 hours = 10:00 PM, then minus 15 minutes = 9:45 PM. Going to bed at 9:45 PM will help you wake up naturally at 7:00 AM.

Frequently Asked Questions