Fitness
Sleep Cycle Calculator
Plan how long to sleep so you wake at the end of a sleep cycle and feel rested.
Time in Bed Needed
β
How It Works
Time = Cycles Γ 1.5 hours + 0.25 hours to fall asleep. A full sleep cycle lasts about 90 minutes; waking at the end of one leaves you far less groggy than waking mid-cycle.
Example
5 cycles = 7.5 hours of sleep + 15 minutes to fall asleep = 7.75 hours in bed. Going to bed at 11 PM, set the alarm for about 6:45 AM.
Frequently Asked Questions
How many sleep cycles do I need?
Most adults do best with 5β6 cycles (7.5β9 hours). Teens need 6+ cycles; short sleepers may manage on 4.
Why wake at the end of a cycle?
Deep sleep occurs mid-cycle. An alarm during deep sleep causes sleep inertia β that heavy grogginess that can last an hour.
Do the 15 minutes to fall asleep matter?
The average sleep latency is 10β20 minutes. If you routinely fall asleep in under 5 minutes, you are probably sleep-deprived.