Sleep Calculator

How Sleep Cycles Work

Sleep occurs in 90-minute cycles, each consisting of light sleep, deep sleep, and REM sleep. Waking up between cycles (rather than in the middle of one) helps you feel refreshed and alert instead of groggy.

Most adults need 5-6 complete cycles (7.5-9 hours) per night. Consistently getting fewer than 4 cycles (6 hours) is associated with impaired cognitive function, weakened immunity, and increased disease risk.

Tips for Better Sleep

• Keep a consistent schedule: Go to bed and wake up at the same time every day, even on weekends.
• Avoid screens before bed: Blue light from phones and computers suppresses melatonin production.
• Cool your room: The optimal sleep temperature is 60-67°F (15-19°C).
• Limit caffeine after 2 PM: Caffeine has a half-life of 5-6 hours and can disrupt sleep quality even if you fall asleep fine.
• Exercise regularly: But finish intense workouts at least 3 hours before bedtime.

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