Sleep CalculatorWhat time should I go to bed or wake up? Based on sleep cycles
Find the best bedtime for your wake-up time, or the best wake-up time for your bedtime, so you wake at the end of a sleep cycle. It adjusts for your age group and how long you take to fall asleep. Reviewed by a pharmacist.
- Pharmacist reviewed
- AASM/CDC age guidance
- Adjustable cycle & latency
- Night hypnogram
Sleep calculator
Most adults’ cycles run 80–110 minutes. If you usually wake before your alarm, try a shorter cycle.
Go to bed at
Your night, cycle by cycle
A simplified hypnogram for the recommended option. Deep sleep (N3) comes mostly in the first cycles, while REM grows longer toward morning. Waking at the top of a wave, out of light sleep, is what helps you feel refreshed.
What time should I go to bed?
Count back from your wake-up time in 90-minute sleep cycles, then subtract about 15 minutes to fall asleep. To wake at 6:30 AM after five cycles (7.5 hours of sleep), go to bed at 10:45 PM. Six cycles (9 hours) means 9:15 PM. Adults need at least 7 hours a night, so the 4-cycle (6-hour) option should be the exception, not the routine.
Bedtime chart by wake-up time
Includes 15 minutes to fall asleep and 90-minute cycles. The 5-cycle column (7.5 h) suits most adults.
| Wake up at | 6 cycles (9 h) | 5 cycles (7.5 h) | 4 cycles (6 h) |
|---|---|---|---|
| 5:00 AM | 7:45 PM | 9:15 PM | 10:45 PM |
| 5:30 AM | 8:15 PM | 9:45 PM | 11:15 PM |
| 6:00 AM | 8:45 PM | 10:15 PM | 11:45 PM |
| 6:30 AM | 9:15 PM | 10:45 PM | 12:15 AM |
| 7:00 AM | 9:45 PM | 11:15 PM | 12:45 AM |
| 7:30 AM | 10:15 PM | 11:45 PM | 1:15 AM |
| 8:00 AM | 10:45 PM | 12:15 AM | 1:45 AM |
How much sleep do you need by age?
Recommendations from the American Academy of Sleep Medicine and Sleep Research Society, as summarized by the CDC.
| Age group | Recommended sleep per 24 hours |
|---|---|
| Infant (4–12 months) | 12–16 hours (including naps) |
| Toddler (1–2 years) | 11–14 hours (including naps) |
| Preschool (3–5 years) | 10–13 hours (including naps) |
| School age (6–12 years) | 9–12 hours |
| Teen (13–18 years) | 8–10 hours |
| Adult (18–60 years) | 7 or more hours |
| Adult (61–64 years) | 7–9 hours |
| Adult (65+ years) | 7–8 hours |
A pharmacist’s notes on better sleep
Caffeine lasts longer than you think
Caffeine’s half-life is about 5 hours in healthy adults, and longer in pregnancy and with some medicines. In a sleep-lab study, a dose taken 6 hours before bed still cut sleep by about an hour. Stop caffeine by early afternoon.
Be careful with OTC sleep aids
Diphenhydramine and doxylamine (“PM” products) often cause next-day grogginess. The AGS Beers Criteria advise older adults to avoid them. Use them occasionally, not nightly, and ask your pharmacist about interactions.
Alcohol fragments sleep
A nightcap may help you fall asleep, but it suppresses REM and causes awakenings in the second half of the night, exactly when your longest REM cycles should happen.
Consistency beats precision
Cycle timing is approximate. A fixed wake time every day, including weekends, does more for your sleep than any calculator. See a clinician about snoring, gasping or ongoing insomnia.
Related calculators
Better sleep is more than one number. These tools complete the picture:
More Sleep & Daily Routine calculators in this cluster:
Manzoor Ahmad
Pharmacist · Calculator Developer · Founder of DexoCalc
I’m a pharmacist with over 9 years of experience writing about health and supplements, and I own a community pharmacy where questions about sleep aids come up every week. I built this calculator on the 90-minute cycle model and the AASM/CDC age recommendations. I wrote the pharmacist notes on caffeine, OTC sleep aids and alcohol from daily practice. It’s an educational tool, not a diagnosis.
Published · Last reviewed · Author profile · Report an issue
Sleep calculator: frequently asked questions
Aim for 10:15 PM (5 cycles, 7.5 hours) or 8:45 PM (6 cycles, 9 hours). Both include about 15 minutes to fall asleep.
About 90 minutes on average, ranging from roughly 80 to 110 minutes between people and across the night. Each cycle moves through light sleep (N1, N2), deep sleep (N3) and REM.
7.5 hours. Adults need at least 7 hours for health. Six hours of well-timed sleep can feel easier to wake from, but it still builds up sleep debt over time.
You may have woken during deep sleep (sleep inertia), had fragmented sleep, or have an untreated sleep disorder. Try aligning your alarm with a cycle end, and see a clinician if it persists.
Yes. The default is 15 minutes, the typical sleep latency for adults. Change it if you usually take longer.
About 6 hours or more before bed. Caffeine’s half-life is around 5 hours, so half of a 3 PM coffee is still in your system at 8 PM.
Use the nap calculator. Naps follow different rules, with 10–20-minute power naps or a full 90-minute cycle.
Sources & references
- About Sleep: how much sleep do I need?, Centers for Disease Control and Prevention
- Recommended Amount of Sleep for a Healthy Adult (AASM/SRS consensus), Journal of Clinical Sleep Medicine, 2015
- Recommended Amount of Sleep for Pediatric Populations (AASM consensus), Journal of Clinical Sleep Medicine, 2016
- Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed, Journal of Clinical Sleep Medicine, 2013
- Physiology, Sleep Stages, StatPearls, NCBI Bookshelf
For general education only, not medical advice. Persistent insomnia, loud snoring, gasping in sleep or excessive daytime sleepiness should be evaluated by a healthcare professional. Talk to your pharmacist before combining sleep aids with other medicines.