Sleep Calculator

A complete sleep cycle lasts approximately 90 minutes and includes 4 stages: light sleep (N1), deeper sleep (N2), deep sleep (N3/slow wave), and REM sleep. Waking up at the end of a cycle (during light sleep) helps you feel more refreshed than waking mid-cycle.

Most adults need 5-6 cycles per night (7.5-9 hours). The National Sleep Foundation recommends 7-9 hours for adults. Getting fewer than 4 cycles (6 hours) regularly is associated with health risks including weakened immunity and impaired cognitive function.

You may be waking up in the middle of a sleep cycle, particularly during deep sleep (N3) or REM. This is called sleep inertia. Try adjusting your wake time by 15-30 minutes to align with the end of a cycle. Also consider sleep quality factors like caffeine, screen time, and room temperature.

The average person takes about 10-20 minutes to fall asleep, called sleep onset latency. This calculator accounts for a 15-minute fall-asleep time. If you consistently fall asleep in less than 5 minutes, you may be sleep-deprived. If it takes more than 30 minutes, you may have insomnia.