Free Sleep Calculator
Calculate optimal bedtimes and wake times based on 90-minute sleep cycles
Calculate your perfect sleep schedule
Based on 90-minute sleep cycles and 15 minutes to fall asleep
We'll calculate the best bedtimes for you We'll calculate when you should wake up
Best times to go to bed: Best times to wake up:
Click a time card to select it
Your sleep schedule
sleep cycles (h m)
Sleep Hygiene Tips
Optimize your sleep quality
Consistent Schedule
Go to bed and wake up at the same time every day, even on weekends. This reinforces your circadian rhythm.
Limit Screen Time
Avoid screens 1 hour before bed. Blue light suppresses melatonin production and delays sleep onset.
Dark Environment
Keep your bedroom dark and cool (65-68F/18-20C). Use blackout curtains if needed.
Avoid Caffeine Late
Stop caffeine consumption 6+ hours before bed. Its half-life means it stays in your system longer than you think.
Bedtime Routine
Create a relaxing routine: reading, stretching, or meditation. This signals your body it is time to sleep.
Morning Light
Get bright light exposure in the morning. This helps reset your circadian clock and improves sleep quality at night.
Understanding Sleep Cycles
Sleep is not a uniform state - your brain cycles through distinct stages throughout the night. Understanding these cycles can help you optimize your sleep and wake up feeling more refreshed. Our sleep calculator uses this science to recommend the best times for you to go to bed or wake up.
The Anatomy of a Sleep Cycle
Each sleep cycle lasts approximately 90 minutes and consists of four distinct stages:
- Stage 1 (N1): Light sleep lasting 5-10 minutes. Your body begins to relax, and you can be easily awakened.
- Stage 2 (N2): Deeper sleep lasting about 20 minutes. Heart rate slows, body temperature drops, and brain waves slow with brief bursts of activity.
- Stage 3 (N3): Deep sleep (slow-wave sleep) lasting 20-40 minutes. This is the most restorative stage where tissue repair, immune function enhancement, and growth hormone release occur.
- REM Sleep: Rapid Eye Movement sleep lasting 10-60 minutes. This is when most dreaming occurs, and it is crucial for memory consolidation and emotional processing.
Why 90-Minute Cycles Matter
The key to waking up refreshed is timing your alarm to coincide with the end of a sleep cycle, when you are in lighter sleep. Waking up during deep sleep (Stage 3) causes sleep inertia - that groggy, disoriented feeling that can last for 30 minutes or more. By aligning your wake time with the natural end of a cycle, you can minimize this effect.
How Much Sleep Do You Need?
Sleep needs vary by age. Here are the recommended hours based on research from the National Sleep Foundation:
Infants (4-12 mo)
12-16 hours
Children (6-12 yr)
9-12 hours
Teens (13-18 yr)
8-10 hours
Adults (18-60 yr)
7-9 hours
Older Adults (61+)
7-8 hours
Athletes
9-10 hours
In terms of sleep cycles:
- 4 cycles (6 hours): Minimum for cognitive function, but not ideal long-term
- 5 cycles (7.5 hours): Good for most adults
- 6 cycles (9 hours): Ideal for athletes, teens, and those recovering from sleep debt
The Role of REM Sleep
REM sleep periods get longer as the night progresses. Your first REM period might last only 10 minutes, while later ones can extend to an hour. This is why sleeping less than 6 hours significantly reduces REM sleep, affecting memory, learning, and emotional regulation. Our calculator helps ensure you get enough complete cycles to benefit from adequate REM sleep.
How to Use This Tool
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1
Choose your mode: "Wake Up At" or "Sleep At"
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2
Select your target time using the time picker
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3
View multiple sleep cycle options (4, 5, or 6 full cycles)
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4
Green highlighted times show recommended 7-9 hours of sleep
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5
Account for 15 minutes to fall asleep (automatically calculated)
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6
Save your preferred sleep schedule for quick access
Frequently Asked Questions
A sleep cycle is a pattern your brain goes through during sleep, consisting of light sleep, deep sleep, and REM (dream) sleep. Each complete cycle takes approximately 90 minutes. Waking up at the end of a cycle, rather than in the middle of deep sleep, helps you feel more refreshed and alert.
The average person takes about 15 minutes to fall asleep after getting into bed. This is called sleep latency. Our calculator accounts for this time so your sleep cycles align properly with when you actually fall asleep, not just when you go to bed.
Adults typically need 7-9 hours of sleep per night, which equals 4-6 complete 90-minute sleep cycles. Our calculator highlights times that fall within this recommended range. However, individual needs vary - some people function well on 6 hours while others need 9.
Waking up during deep sleep (in the middle of a cycle) often causes sleep inertia - that groggy, disoriented feeling. By timing your wake-up to coincide with the end of a sleep cycle when you are in lighter sleep, you are more likely to wake up feeling refreshed.
While completing full sleep cycles helps you wake up feeling better, getting enough total sleep is still important. Aim for at least 4-5 complete cycles (6-7.5 hours). Consistently getting less than 6 hours of sleep can lead to sleep debt and health issues.
Yes! Each 90-minute cycle includes a REM (Rapid Eye Movement) phase where dreaming occurs. REM sleep is crucial for memory consolidation and emotional processing. Later cycles in the night have longer REM periods, which is why getting 5-6 full cycles is optimal.
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