During sleep, light (REM) and deep (non-REM) sleep alternate in cycles of roughly 90 minutes. If your alarm rings during deep sleep you tend to feel groggy, while waking at a cycle boundary (light sleep) makes it easier to feel refreshed. This tool calculates the best bedtime or wake-up time from that rhythm.
How to use this tool
Enter your wake-up time and you get bedtime options for 4–6 cycles (6, 7.5 and 9 hours of sleep). Or, going to bed now? Enter your bedtime and get the best times to wake. Both include an average 15 minutes to fall asleep.
Sleep and strength training
Growth hormone — key to muscle repair — is secreted most during the deep non-REM sleep just after falling asleep. Sleep deprivation lowers testosterone, disrupts appetite and hurts training quality, which is why sleep is often called the third pillar of training (exercise, nutrition, rest). 7–9 hours is the common recommendation.
Tips
Keeping consistent bed and wake times stabilizes your cycles and improves mornings. Recovery also needs nutrition — check daily calories with the TDEE Calculator and protein with the Protein Calculator.
What is a sleep cycle?+
A cycle averages about 90 minutes (typically 80–110 minutes between individuals) and repeats 4–6 times a night. Waking during light sleep tends to feel more refreshing.
Why 90 minutes?+
Cycle length varies between people and from night to night, so use the results as a starting point and fine-tune over a few days to find what feels best.
How many hours of sleep are best?+
Consistently sleeping under 6 hours (4 cycles) tends to hurt focus, metabolism and muscle recovery.
Should I sleep more on training days?+
Growth hormone release is concentrated in the deep sleep right after falling asleep, so keeping a consistent bedtime matters most on training days. Some reports recommend around 9 hours for athletes.
Does this work for naps?+
A 90-minute nap counts as one full cycle, but long naps late in the day can interfere with night sleep and are best avoided.
・Hirshkowitz M, et al. (2015). National Sleep Foundation's sleep time duration recommendations. Sleep Health, 1(1), 40–43.
・Carskadon MA, Dement WC. (2011). Normal Human Sleep: An Overview. In: Principles and Practice of Sleep Medicine, 5th ed.
・Van Cauter E, Plat L. (1996). Physiology of growth hormone secretion during sleep. The Journal of Pediatrics, 128(5), S32–S37.
Sleep-cycle length and sleep needs vary between individuals; results are guides based on population averages. If you have persistent sleep problems such as insomnia, oversleeping or strong daytime sleepiness, please consult a medical professional.
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