Sleep Cycle Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles.
21:16
Bedtime — 9.0h sleep
22:46
Bedtime — 7.5h sleep
00:16
Bedtime — 6.0h sleep
01:46
Bedtime — 4.5h sleep
Each cycle is 90 minutes. Assumes 14 minutes to fall asleep. 5–6 cycles (7.5–9 hrs) is ideal for most adults.
How the Sleep Cycle Calculator Works
This calculator suggests bedtimes or wake-up times that align with complete 90-minute sleep cycles, so you're more likely to wake up during lighter sleep rather than mid-deep-sleep.
It works backward (or forward) from your target time in increments of 90 minutes for 3 to 6 full cycles, then adds 14 minutes to account for the average time it takes to fall asleep.
Example: If you want to wake up at 6:30 AM, 5 cycles (7.5 hours of sleep) means going to bed at 10:46 PM, while 6 cycles (9 hours) means going to bed at 9:16 PM.