😴 Sleep Calculator
Find the best bedtime or wake time for full sleep cycles
How Sleep Cycle Calculation Works
Formula
Wake Time = Bedtime + (90 min × Number of Cycles) + 15 min fall-asleep time
- 1Enter your desired wake-up time or bedtime.
- 2The calculator accounts for ~15 minutes to fall asleep.
- 3Each sleep cycle lasts approximately 90 minutes.
- 4Ideal sleep is 5-6 complete cycles (7.5-9 hours).
- 5Suggested times align with cycle endings to minimize grogginess.
About Sleep Calculator
Calculate the best times to fall asleep or wake up based on sleep cycles. Optimize your rest by waking between cycles. Avoid grogginess with science-based sleep timing.
Frequently Asked Questions
Why do I feel groggy even after 8 hours of sleep?
You likely woke up in the middle of a sleep cycle. Each cycle is about 90 minutes. Waking between cycles (after 7.5 or 9 hours) feels more refreshing than waking mid-cycle at 8 hours.
How many sleep cycles do I need?
Most adults need 5-6 complete sleep cycles per night, which equals 7.5-9 hours. Some people function well on 5 cycles (7.5 hours) while others need 6 (9 hours).
How long does it take to fall asleep?
The average person takes 10-20 minutes to fall asleep. The calculator uses 15 minutes as a default. If you fall asleep faster or slower, adjust accordingly.