Sleep Cycles
Calculator
Results
- Wake time
- 07:00
- Five-cycle bedtime option
- 23:15
Bedtime options counted backward from wake time
- 4 Four-cycle option00:45
- 5 Five-cycle option23:15
- 6 Six-cycle option21:45
Four-to-six-cycle bedtime options
| 4 | 6.00 h | 00:45 |
| 5 | 7.50 h | 23:15 |
| 6 | 9.00 h | 21:45 |
Formula
Tᵦ = T𝓌 − n × d𝒸 − dₗ= 23:15
Note
Sleep cycles vary through the night and between people. These clock options do not predict a wake stage or guarantee sleep quality.
More in Health
See all →Frequently asked questions
How does this calculator determine my ideal sleep or wake time?+
It works backward or forward from a target bedtime or wake time using the average length of a sleep cycle, typically about 90 minutes, and multiplies that by whole cycles to suggest times that align with lighter sleep stages. Waking up between cycles rather than mid-cycle is associated with feeling more rested.
Why does waking up mid-cycle make me feel groggy?+
Sleep cycles move through stages of light sleep, deep sleep, and REM sleep, and being woken during deep sleep in particular can cause a foggy, disoriented feeling known as sleep inertia. Timing your alarm for the end of a cycle, when you're naturally in lighter sleep, tends to reduce this effect.
Is 90 minutes an exact figure for everyone's sleep cycle?+
No, actual cycle length varies between individuals and even from night to night, typically ranging from about 70 to 120 minutes. The 90-minute average used in these calculations is a helpful approximation, not a precise measurement of your personal cycles.
Does this calculator account for the time it takes to fall asleep?+
Most sleep cycle calculators add a buffer, often around 15 minutes, to account for typical sleep onset latency, since you don't fall asleep the instant you lie down. If you tend to take longer or shorter than average to fall asleep, you may need to adjust the suggested time accordingly.
How many sleep cycles should I aim for per night?+
Most adults need about 5 to 6 complete cycles per night, which corresponds to roughly 7.5 to 9 hours of sleep, though individual needs vary with age and lifestyle. Consistently getting fewer cycles than your body needs contributes to cumulative sleep debt over time.