Sleep Cycle Calculator
Calculate the best times to wake up.
What time do you need to wake up?
We'll calculate the best times to go to bed so you wake up at the end of a sleep cycle.
Sleep isn't a uniform state—it's a dynamic process that cycles through distinct stages approximately every 90 minutes. Each complete cycle includes:
- Stage N1: Light sleep, easily awakened (5-10 min)
- Stage N2: Deeper sleep, heart rate slows (10-25 min)
- Stage N3: Deep sleep, body repair occurs (20-40 min)
- REM Sleep: Dreaming, memory consolidation (10-60 min)
Waking during deep sleep (N3) causes sleep inertia—that groggy feeling. By timing your alarm to the end of a cycle (light sleep), you wake feeling naturally refreshed.
Adults (18-64 years)
7-9 hours (5-6 cycles) recommended
Teenagers (14-17 years)
8-10 hours (5-7 cycles) recommended
Older Adults (65+)
7-8 hours (5 cycles) recommended
Individual needs vary. Pay attention to how you feel—if you need an alarm to wake up or feel drowsy during the day, you may need more sleep.
Quality matters as much as quantity. Here are evidence-based tips for better sleep:
- Consistency: Go to bed and wake up at the same time every day
- Light exposure: Get bright light in the morning, dim lights in the evening
- Temperature: Keep your bedroom cool (65-68°F / 18-20°C)
- Limit caffeine: Avoid caffeine after 2 PM (it has a 6-hour half-life)
- Exercise regularly: But not within 3 hours of bedtime
- Screen time: Stop screens 1 hour before bed or use blue light filters
Frequently Asked Questions
A sleep cycle typically lasts about 90 minutes and includes all stages of sleep: light sleep (N1, N2), deep sleep (N3), and REM sleep. Most adults need 4-6 complete cycles per night for optimal rest.
Waking during deep sleep (N3 stage) causes sleep inertia—that groggy, disoriented feeling. By timing your wake-up to the end of a sleep cycle (during light sleep), you'll feel more refreshed and alert.
The average person takes about 10-20 minutes to fall asleep. This calculator uses 15 minutes as a default. If you fall asleep faster or slower, adjust your bedtime accordingly.
Most adults need 7-9 hours (5-6 sleep cycles). Teenagers need 8-10 hours, and children need even more. Quality matters as much as quantity—5 complete cycles may leave you more rested than 8 hours of interrupted sleep.
The times are suggestions—don't stress if you miss them. If you're not tired at the calculated bedtime, try the next cycle option (90 minutes later). Forcing sleep when you're not tired often backfires.
Yes! For naps, aim for either 20 minutes (before deep sleep) or 90 minutes (one full cycle). Avoid 30-60 minute naps as you'll likely wake during deep sleep feeling worse than before.
Sleep Health Notice
This calculator provides general guidance based on average sleep cycle duration. Individual cycles can vary from 70-120 minutes. If you experience persistent sleep problems, excessive daytime sleepiness, or suspect a sleep disorder, consult a healthcare provider or sleep specialist.