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Sleep Cycle Calculator
Calculate the best times to wake up or go to sleep based on 90-minute sleep cycles.
Choose whether you are setting a wake-up time or a bedtime.
Select the hour.
Select the minute.
About This Tool
This sleep cycle calculator helps you time your bedtime or wake-up so you finish a complete 90-minute sleep cycle instead of waking mid-cycle feeling groggy. Whether you need 5 cycles or 6, aligning your schedule to these natural rhythms is the key to waking sharp and rested. Pair this with our Caffeine Cutoff Calculator to make sure your last cup of coffee is not sabotaging your sleep quality.
How to Use
Choose whether to calculate a bedtime or wake-up time, then enter the time. The sleep cycle calculator adds 15 minutes to fall asleep and works in 90-minute cycles to give you four options. Pick the time that fits your schedule — 5 or 6 full cycles is ideal for recovery and performance.
FAQ
Why 90-minute cycles instead of 8 hours?
Each sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM. Waking between cycles lets you feel alert immediately. Waking mid-cycle causes sleep inertia — that heavy, disoriented feeling — even after a long night. Timing your sleep around complete cycles matters more than total hours.
How many sleep cycles do I actually need?
Most adults need 5-6 full cycles (7.5-9 hours) per night for optimal health and recovery. You can manage 4 cycles occasionally, but chronic short sleep is linked to lower testosterone, impaired muscle recovery, and poor decision-making. On training days, aim for 5 cycles minimum.
What if I take longer than 15 minutes to fall asleep?
The 15-minute estimate works for most healthy adults. If you regularly take longer, go to bed earlier by the difference. Reducing screen time 30 minutes before bed and keeping your room cool (65-68 F) helps. Our Caffeine Cutoff Calculator can also help identify if late caffeine is the culprit.
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