Sleep cycle
1 cycle = 90 minutes; results use 5, 6, and 7 cycles.
Sleep Calculator
Optimal Sleep
Calculate optimal wake-up or bedtime based on 90-minute sleep cycles.
Recommended Times (by cycle)
5 cycles
06:44
7.5h
6 cycles
08:14
9h
7 cycles
09:44
10.5h
Includes ~14 min to fall asleep
Chronotype
Intermediate: Aim for 10–11pm bedtime, 7–8am wake.
Sleep Debt Calculator
Sleep Debt-1.0h
Sleep planning works best when duration, cycles, and time to fall asleep are considered together
This calculator uses 90-minute sleep cycles and an average 14-minute time to fall asleep to work forward from bedtime or backward from wake-up time. It also includes chronotype guidance and a simple sleep-debt estimate from last night's sleep.
Calculation basics
Sleep onset
About 14 minutes is added or subtracted for falling asleep.
Sleep debt
Shows the difference between an 8-hour target and actual sleep.
How to use
- Choose bedtime-to-wake or wake-to-bed mode.
- Enter the reference time and compare the three suggested times.
- Add chronotype and last night's actual sleep to set a realistic target.
Frequently asked questions
Is a 90-minute sleep cycle exact for everyone?
No. It is a practical average; individual sleep-stage timing can vary.
Will waking at a suggested time guarantee feeling refreshed?
No. Sleep quality, light exposure, caffeine, stress, and accumulated sleep loss also matter.
Can weekend sleep erase sleep debt?
Some recovery is possible, but a regular schedule is more reliable. Persistent sleepiness deserves medical attention.
Results are general estimates and are not a substitute for professional medical advice about sleep disorders or health concerns.