Sleep Calculator
Calculate optimal bedtimes or wake times based on 90-minute sleep cycles. Waking at the end of a cycle helps you feel more refreshed.
Choose whether you want to wake up at a specific time or go to sleep at a specific time. The calculator shows four to six options based on 3 to 6 full sleep cycles.
Sleep Cycle Calculator
Human sleep follows a roughly 90-minute cycle, moving through light sleep, deep sleep, and REM stages. Waking up at the end of a complete cycle — rather than in the middle of deep sleep — can help you feel more alert and rested. This calculator adds a 15-minute buffer to account for the average time it takes to fall asleep.
How to Use
- Select wake up at to find the best bedtime for your desired wake time, or go to sleep at to find the best wake time for your desired bedtime.
- Set the time using the time picker. Results update immediately.
- Recommended options (5 or 6 cycles) are highlighted with a purple border.
Sleep Cycle Durations
- 3 cycles = 4.5 hours (short sleep)
- 4 cycles = 6 hours (moderate)
- 5 cycles = 7.5 hours (recommended)
- 6 cycles = 9 hours (recommended)
Frequently Asked Questions
How does the sleep calculator determine the best bedtime?
The sleep calculator works on 90-minute sleep cycles. It counts backward from your desired wake time in 90-minute increments, plus a 15-minute buffer to fall asleep. Waking at the end of a cycle helps you feel more refreshed.
How many sleep cycles do I need?
Most adults benefit from 5 to 6 full sleep cycles (7.5 to 9 hours). The calculator recommends 5 or 6 cycles as optimal. Fewer cycles (3 or 4) can work for naps or when time is limited.
What is the 15-minute buffer?
The average person takes about 15 minutes to fall asleep after getting into bed. The calculator adds this buffer so that the sleep cycles align with your actual sleep time, not your bedtime.
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