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Sleep Cycle Calculator

Find the best time to go to bed or wake up based on natural 90-minute sleep cycles. Wake up feeling refreshed instead of groggy by timing your sleep correctly.

✅ Science-Based 😴 Better Sleep ⏰ Smart Timing 🆓 Free Forever

Sleep Calculator

We'll calculate the best times to wake up based on complete sleep cycles.

We'll calculate the best times to go to bed to wake up refreshed.

Your Sleep Schedule

📚 Understanding Sleep Cycles

What Are Sleep Cycles?

Sleep isn't one continuous state—it happens in cycles that last about 90 minutes each. During each cycle, you go through different stages of sleep, from light sleep to deep sleep to REM (Rapid Eye Movement) sleep.

The 4 Stages of Sleep:

  • Stage 1 (Light Sleep): Transition between wakefulness and sleep (5-10 minutes)
  • Stage 2 (Light Sleep): Body temperature drops, heart rate slows (10-25 minutes)
  • Stage 3 (Deep Sleep): Most restorative sleep, hard to wake up from (20-40 minutes)
  • REM Sleep: Dreaming occurs, brain is active (10-60 minutes)

Why 90-Minute Cycles Matter:

Waking up during deep sleep (Stage 3) makes you feel groggy and disoriented—that's called "sleep inertia." Waking up at the end of a complete cycle (during light sleep or REM) helps you feel more alert and refreshed.

How Much Sleep Do You Need?

  • Adults (18-64): 7-9 hours (4-6 complete cycles)
  • Teenagers (14-17): 8-10 hours (5-6 cycles)
  • Older Adults (65+): 7-8 hours (4-5 cycles)

Note: These are general guidelines. Individual sleep needs vary.

Tips for Better Sleep:

  • Keep a consistent sleep schedule (same bedtime and wake time)
  • Avoid screens 30-60 minutes before bed (blue light disrupts sleep)
  • Keep your bedroom cool, dark, and quiet
  • Avoid caffeine after 2 PM
  • Get regular exercise, but not right before bed
  • Don't eat heavy meals close to bedtime

❓ Frequently Asked Questions

The calculator is based on the well-established science of 90-minute sleep cycles. However, individual sleep cycles can vary slightly (80-110 minutes). Use this as a helpful guide, but pay attention to how you actually feel when you wake up.

You might be waking up in the middle of a deep sleep cycle. Try using this calculator to wake up at the end of a complete cycle instead. Also, sleep quality matters as much as quantity—factors like stress, sleep apnea, or an uncomfortable sleeping environment can affect how rested you feel.

The average person takes about 10-20 minutes to fall asleep. This calculator assumes 14 minutes, which is already factored into the suggested times. If you consistently take much longer to fall asleep, you might want to adjust the times accordingly.

For most adults, 6 hours (4 complete cycles) is on the lower end and may not be enough for optimal health and performance. Most adults need 7-9 hours. However, some people function well on 6 hours. Listen to your body and see how you feel during the day.

Use it to find a sleep schedule that works for you, then try to stick to that schedule consistently. Consistency is more important than perfection. Once you find wake times that make you feel good, set those as your regular alarm times.

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