Sleep Cycle Calculator
Find the best bedtime or wake time to align with the end of a 90-minute sleep cycle.
What is Sleep Cycle?
Most adult sleep cycles last about 90 minutes. Waking at the end of a cycle (when sleep is light) feels much more refreshing than waking mid-cycle from deep sleep. By picking a bedtime that lands you 4, 5 or 6 cycles before your alarm — plus the 15 minutes most people take to fall asleep — you wake at the bottom of the cycle.
How is it calculated?
Bedtime = wake time − (cycles × 90 min) − 15 min. Wake time = bedtime + (cycles × 90 min) + 15 min. Five cycles (~7.5 hours) is the sweet spot for most adults.
Frequently Asked Questions
- Are 90-min cycles exact?
- They average 90 min but vary 70–110 min.
- Should I avoid 6 cycles?
- No — 6 cycles (9h) is great for teens and recovering athletes.
- What about naps?
- 20-min or 90-min naps work best.