Sleep Calculator
Calculate optimal sleep and wake times
Note: Sleep cycles last about 90 minutes. Waking up between cycles helps you feel more refreshed. It takes about 14 minutes to fall asleep.
Frequently Asked Questions
How does the sleep calculator work?
The calculator is based on 90-minute sleep cycles. During sleep, you go through several cycles of light and deep sleep. Waking up at the end of a cycle (not in the middle) helps you feel more refreshed. The calculator adds 14 minutes for falling asleep time.
How many sleep cycles do I need?
Most adults need 4-6 complete sleep cycles per night (6-9 hours). The calculator shows options for 4, 5, and 6 cycles. Five cycles (7.5 hours) is optimal for most people, but individual needs vary by age, activity level, and health.
Why do I still feel tired after sleeping 8 hours?
You might be waking up in the middle of a sleep cycle. Even with 8 hours of sleep, waking during deep sleep can cause grogginess. Try using the calculator to wake at the end of a cycle - you may feel more refreshed with slightly less total sleep time.