Sleep Cycle Calculator
Online sleep cycle calculator: based on 90-minute sleep cycles and accounting for the time it takes to fall asleep, it estimates the ideal bedtime or wake-up time to reduce grogginess—great for planning your schedule.
Each cycle is about 90 minutes; 5–6 cycles (7.5–9 hours) are recommended. Falling asleep takes about 15 minutes, which is already accounted for.
Calculated on the basis of a 90-minute sleep cycle with 15 minutes allowed for falling asleep, to help you wake during light sleep.
The result is for schedule reference only; individual differences are large, so adjust based on how you feel.