Wake up refreshed by aligning your sleep with your natural 90-minute cycles. Tell us when you need to wake up, and we'll calculate the perfect bedtime.
Click calculate to see recommended bedtimes
Focus on getting through full 90-minute cycles even if you sleep less total hours. Waking up mid-cycle is what makes you feel groggy even after a long sleep.
Your body doesn't just switch off during sleep. It cycles through light, deep, and REM sleep every 90 minutes. Each stage serves a different purpose, especially brain and muscle recovery.
When you wake up at the end of a cycle, you feel refreshed and energized because you've allowed your brain to complete its natural housekeeping process.
The feeling of "sleep inertia"—the grogginess that follows waking up—happens because you've been pulled out of a deep sleep stage before your brain was ready.
This leaves your brain in a fog, as it struggles to switch from deep-sleep mode to awake mode. Aligning your wake time with the end of a cycle avoids this fog.
Most healthy adults take about 14-16 minutes to fall into sleep. This calculator accounts for that buffer, recommended when selecting a bedtime.
If you know it takes you longer, start your bedtime routine earlier. Your body needs that downtime to lower your heart rate and prepare for rest.
Beyond timing, environment matters. Try these for a better sleep:
While 90 minutes is the average sleep cycle duration, it can vary from 70 to 110 minutes depending on age, genetics, and individual biology. Young adults typically have cycles closer to 90 minutes, while older adults may experience slightly shorter cycles. The key is to wake up at the end of a complete cycle rather than in the middle of deep sleep.
If you find yourself unable to fall asleep at the suggested time, don't worry. The calculator accounts for a 15-minute buffer for falling asleep. If you're still awake after 20-30 minutes, try reading a book or doing a calming activity until you feel drowsy. You can also use the "Sleep Now" mode to calculate wake-up times if you're going to bed immediately.
Feeling tired despite completing sleep cycles can be due to several factors: sleep quality issues (noise, light, temperature), underlying health conditions, stress, or not getting enough total sleep. Quality matters as much as timing. Ensure your sleep environment is dark, cool, and quiet. If fatigue persists, consider consulting a healthcare professional to rule out sleep disorders like sleep apnea.
Yes! For naps, aim for 90 minutes (one complete cycle) or multiples of 90 minutes. A 20-30 minute power nap can also be effective if you wake before entering deep sleep. However, avoid napping too close to your regular bedtime, as it can interfere with nighttime sleep. The best nap time is usually midday, between 1-3 PM.
The Sleep Tracker stores your sleep data locally in your browser and calculates duration based on the times you log. It provides valuable insights into your sleep patterns over time. However, for more detailed sleep analysis including REM cycles, deep sleep stages, and sleep quality metrics, consider using dedicated sleep tracking devices or apps that monitor your actual sleep stages.