Free Sleep Cycle Calculator
Calculate optimal bedtimes based on your wake-up time and 90-minute sleep cycles. Waking at the end of a cycle helps you feel more rested.
hour
Use 24-hour format (e.g., 7 = 7 AM, 22 = 10 PM)
min
Bedtime (5 cycles / 7.5 hrs) - Recommended
23.50 hour (decimal)
Bedtime (6 cycles / 9 hrs)22.00 hour (decimal)
Bedtime (4 cycles / 6 hrs)1.00 hour (decimal)
Ideal Sleep Duration7.5 hours
Bedtime (5 cycles / 7.5 hrs) - Recommended vs Wake-up Hour (24h)
Sleep Cycles
One complete sleep cycle lasts approximately 90 minutes. Most adults need 5-6 complete cycles per night.
Waking between cycles (rather than mid-cycle) helps you feel more refreshed.
Example Calculation
Waking up at 7:00 AM.
- 01Wake time = 7:00 = 420 minutes
- 026 cycles: 420 - 540 = -120 min => (-120 + 1440) / 60 = 22.0 (10:00 PM)
- 035 cycles: 420 - 450 = -30 min => (-30 + 1440) / 60 = 23.5 (11:30 PM)
- 044 cycles: 420 - 360 = 60 min => 60 / 60 = 1.0 (1:00 AM)
Frequently Asked Questions
Learn More
Understanding BMI: What It Means and How to Calculate It
Learn what BMI is, how to calculate it, what the ranges mean, and the limitations of body mass index as a health metric. Comprehensive guide with formulas and context.