Sleep Calculator
Find your ideal bedtime or wake-up time based on 90-minute sleep cycles. Wake up refreshed, not groggy.
Bedtime Calculator
What time do you want to wake up?
Wake-up Time Calculator
What time are you going to bed?
Sleep Duration Calculator
How many sleep hours & cycles did you get?
Sleep Calculator by Age — Recommended Hours
How much sleep you need changes with age. These are the CDC recommendations.
| Age Group | Recommended Sleep | Sleep Cycles |
|---|---|---|
| Newborns (0–3 months) | 14–17 hours | 9–11 cycles |
| Infants (4–12 months) | 12–16 hours | 8–10 cycles |
| Toddlers (1–2 years) | 11–14 hours | 7–9 cycles |
| Preschool (3–5 years) | 10–13 hours | 6–8 cycles |
| School-age (6–12 years) | 9–12 hours | 6–8 cycles |
| Teenagers (13–18 years) | 8–10 hours | 5–6 cycles |
| Adults (18–60 years) | 7+ hours | 5–6 cycles |
| Older Adults (61–64 years) | 7–9 hours | 4–6 cycles |
| Seniors (65+ years) | 7–8 hours | 4–5 cycles |
How the 90-Minute Sleep Cycle Works
Non-REM Sleep
The first part of each cycle. Your body repairs tissue, boosts immunity, and builds energy. Deep sleep is most restorative.
REM Sleep
Rapid Eye Movement sleep consolidates memory, processes emotions, and is when vivid dreaming occurs. Vital for mental health.
The 90-Min Cycle
Each full cycle lasts ~90 minutes. Waking between cycles feels natural and energized. 5–6 cycles per night is optimal for adults.
Frequently Asked Questions
How does the sleep calculator work?
This sleep cycle calculator adds 15 minutes (average time to fall asleep) plus multiples of 90 minutes (one full sleep cycle) to your bedtime or wake-up time. Waking at the end of a cycle means lighter sleep, so you feel refreshed rather than groggy.
What is a 90-minute sleep cycle?
A sleep cycle is the oscillation between non-REM and REM sleep, averaging 90 minutes per cycle. A complete night of sleep consists of 4–6 full cycles. Our REM cycle calculator helps you time your alarm to land between cycles.
How much sleep do adults need?
The CDC recommends adults aged 18–60 get 7 or more hours per night, equivalent to 5–6 sleep cycles. Older adults (65+) need 7–8 hours. Use the sleep calculator by age table above for specific guidelines.
Why do I still feel tired after 8 hours of sleep?
Waking in the middle of a deep sleep cycle (non-REM stage 3) causes “sleep inertia” — that groggy feeling. Use this bedtime calculator to time your wake-up at the end of a complete 90-minute cycle, even if total sleep is slightly shorter.
What is sleep debt and how do I calculate it?
Sleep debt is the cumulative effect of not getting enough sleep. If you need 8 hours but only get 6, you accumulate 2 hours of sleep debt per night. Use the Duration tab to check your actual sleep hours vs. the recommended amount for your age.
What time should I go to sleep to wake up at 6 AM?
To wake at 6:00 AM feeling refreshed: go to sleep at 12:45 AM (5 cycles), 11:15 PM (6 cycles), 9:45 PM (7 cycles), or 8:15 PM (8 cycles). The calculator accounts for 15 minutes to fall asleep.
What is REM sleep and why does it matter?
REM (Rapid Eye Movement) sleep is the final stage of each 90-minute cycle. It is critical for memory consolidation, emotional processing, and creativity. Adults need 20–25% of total sleep in REM — roughly 90–120 minutes per night. Cutting sleep short typically eliminates the REM-rich cycles that occur in the second half of the night.
How long should a nap be?
The optimal nap duration depends on your goal: a 10–20 minute power nap boosts alertness without entering deep sleep; a 90-minute full-cycle nap includes REM and is ideal for memory and creativity. Avoid 30-minute naps — they enter deep sleep (N3) and cause grogginess (sleep inertia) upon waking.
What time should I sleep to wake up at 7 AM?
To wake at 7:00 AM: go to bed at 1:45 AM (5 cycles), 12:15 AM (6 cycles), 10:45 PM (7 cycles), or 9:15 PM (8 cycles). Each option includes 15 minutes to fall asleep. The 6-cycle option (12:15 AM) gives 7.5 hours and is optimal for most adults.
What is the best sleep schedule for teenagers?
The CDC recommends teenagers (13–18) get 8–10 hours per night (5–6+ cycles). Studies show teens have a natural circadian shift that delays melatonin release, making it biologically harder to fall asleep before 11 PM. School start times before 8:30 AM are linked to chronic sleep deprivation in adolescents.
Want to understand the science behind sleep cycles?
Our in-depth guide covers REM sleep, circadian rhythm, sleep debt, polyphasic schedules, and science-backed optimization tips — with affiliate-recommended sleep trackers to help you measure your progress.