Find the best bedtime or wake time based on 90-minute sleep cycles and what your age group actually needs.
What it means
A full sleep cycle moves through light sleep, deep sleep, and REM — roughly 90 minutes on average for adults (kids and infants run shorter). Waking at the end of a cycle, in light sleep, feels easy. Waking mid-deep-sleep is the textbook definition of "groggy." The five options below all land at cycle boundaries.
Healthy sleepers take 10–20 minutes to drift off after lights out. We add 15 to the bedtime so the cycle math reflects when you're actually asleep, not when your head hit the pillow.
Sleep requirements drop sharply through childhood and then stabilize in adulthood. The recommended ranges below come from the National Sleep Foundation's consensus guidelines (Hirshkowitz et al., 2015), which are still the most-cited evidence-based ranges and align closely with the AAP and AASM pediatric recommendations.
FAQ
Real cycles run 70–110 minutes and vary by person, age, and across the night (later cycles tend to be longer with more REM). 90 minutes is the textbook average and the cleanest planning number. If you consistently feel groggy at one option, try the one 15–30 minutes earlier.
Brain development drives sleep need. Newborns spend ~50% of sleep in REM (vs. ~20% for adults), and growth hormone release peaks during deep sleep — so kids genuinely need more. By the 20s, sleep need stabilizes around 7–9 hours. Older adults often see slightly compressed sleep, hence the 7–8 hour upper bound for 65+.
Yes. Sleep before midnight has more deep sleep; sleep after 4 AM has more REM. Both matter. Going to bed at 2 AM and sleeping until 10 AM gives roughly the same hours as 10 PM to 6 AM, but the composition is different — and the misaligned circadian timing has its own costs.
National Sleep Foundation expert consensus (Hirshkowitz et al., Sleep Health, 2015), reaffirmed by subsequent reviews. The pediatric ranges are consistent with the American Academy of Sleep Medicine and AAP joint recommendations (Paruthi et al., 2016).
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Pick "I want to wake up at" or "I want to go to bed at," choose your age, and see five cycle-aligned options. The ones in your recommended range are highlighted.
Each option lands at the end of a sleep cycle. Times in your age range are marked Optimal. Includes 15 minutes to fall asleep.