Sleep Calculator
Find optimal bedtimes or wake times based on 90-minute sleep cycles.
Go to bed at one of these times:
8:16 PM
7 cycles = 10h 30m
9:46 PM
6 cycles = 9h
Recommended11:16 PM
5 cycles = 7h 30m
Recommended12:46 AM
4 cycles = 6h
Based on 14 minutes to fall asleep. Each sleep cycle is approximately 90 minutes.
Sleep Cycles and Why They Matter
A full sleep cycle lasts approximately 90 minutes and includes multiple stages: light sleep (N1, N2), deep sleep (N3, also called slow-wave sleep), and REM (rapid eye movement). Deep sleep is critical for physical recovery; REM sleep supports memory consolidation and emotional processing. Waking during deep sleep causes grogginess (sleep inertia), while waking at the end of a complete cycle helps you feel more refreshed.
How Much Sleep Do You Need?
| Age Group | Recommended Hours | Notes |
|---|---|---|
| Adults (18-64) | 7-9 hours | Most adults need at least 7 |
| Older adults (65+) | 7-8 hours | Sleep tends to lighten with age |
| Teenagers (14-17) | 8-10 hours | Biological clock shifts later |
| School children (6-13) | 9-11 hours | Critical for development |
| Toddlers (1-2 years) | 11-14 hours | Including naps |
Tips for Better Sleep Quality
Keep a consistent sleep schedule, even on weekends. Keep your bedroom cool (65-68 F / 18-20 C) and dark. Avoid screens for 30-60 minutes before bed — blue light delays melatonin production. Limit caffeine after 2-3pm (caffeine half-life is 5-6 hours). Avoid large meals and alcohol close to bedtime. If you can't fall asleep in 20 minutes, get up and do something calm until you feel sleepy.