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About the Sleep Calculator
This Sleep Calculator estimates the best times to fall asleep or wake up based on natural sleep cycles. Enter a wake-up time or a bedtime, and it returns several suggested times arranged around complete cycles. Each result marks when a full cycle ends, so you can pick a time that fits your schedule.
The tool uses the widely applied 90-minute sleep cycle model. It counts backward or forward in 90-minute blocks and adds about 15 minutes for the time it takes to fall asleep. You only need one input: the hour you plan to wake or the hour you go to bed. For smoother mornings, choose a time that ends a cycle rather than one that cuts a cycle short.
- Enter the time you need to wake up or the time you plan to sleep.
- Review the suggested times and pick the one closest to your target rest length.
- Set your alarm for the chosen time and adjust after a few nights if needed.