Sleep Cycle Calculator

Calculate natural 90-minute sleep cycles to wake up feeling refreshed and avoid sleep inertia grogginess.

Optimal Times to Fall Asleep

21:45
6 cycles (9.0 hrs)
Recommended
23:15
5 cycles (7.5 hrs)
Recommended
00:45
4 cycles (6.0 hrs)
02:15
3 cycles (4.5 hrs)