Sleep & Wake Timer
Classic bedtime utility for optimal sleep cycles
How It Works
Sleep Cycles: Each complete sleep cycle lasts 90 minutes. Waking up between cycles (not during deep sleep) makes you feel more refreshed.
Fall Asleep Time: Most people take about 15 minutes to fall asleep after getting into bed.
Optimal Sleep: 5 cycles (7.5 hours) is ideal for most adults. Some need 4 cycles (6h), others 6 cycles (9h).
Classic & Simple: No wellness gimmicks. Just proven sleep science from the Nokia phone era.
Pro Tip
Consistency is key. Try to maintain the same sleep and wake times every day, even on weekends. Your body's circadian rhythm will thank you.
What is the Sleep & Wake Timer?
The Sleep & Wake Timer is a scientifically-based tool for optimizing your sleep-wake rhythm based on sleep cycle theory. Unlike simple sleep calculators, this tool considers the body's natural 90-minute sleep cycles and recommends bedtimes or wake times synchronized with these cycles. The goal: waking up between cycles (light sleep phase) instead of in the middle of deep sleep – for more rest and less groggy feeling in the morning.
The tool offers two modes: (1) "When to wake up" – you enter your planned bedtime and receive optimal wake times, (2) "When to sleep" – you enter your fixed wake time and receive recommended bedtimes. Both modes automatically account for 15 minutes to fall asleep. Recommendations are based on 4-6 complete sleep cycles (6-9 hours), with 5 cycles (7.5h) considered optimal for most adults.
This tool is a modernized version of the classic Sleepyti.me calculator from the Nokia era – proven sleep science without wellness gimmicks. Ideal for people with fixed work hours, shift workers with variable sleep patterns, students with flexible schedules, or anyone who wants to wake up refreshed instead of exhausted. The visualization with sun/moon symbols intuitively shows which times suit which time of day.
How does the Sleep & Wake Timer work?
1. Choose Mode
Decide what you want to plan: Know your bedtime and want to know when you should wake up? Choose "When to wake up". Have a fixed wake time (e.g., alarm at 7 AM) and want to know when you should go to bed? Choose "When to sleep". The mode determines which time you enter and which is calculated.
2. Enter Time
Enter either your planned bedtime or your desired wake time. The tool automatically adds 15 minutes to fall asleep (typical average). If you fall asleep faster (5-10 min) or need longer (20-30 min), consider that mentally with the recommendations. Input updates calculations immediately in real-time.
3. Analyze Recommended Times
The tool shows 4-6 options, corresponding to 4-6 complete sleep cycles. Each option shows the time, total sleep duration, and number of cycles. The middle options (5-6 cycles, 7.5-9h) are highlighted in color as optimal. Choose based on your individual sleep needs: short sleepers prefer 4-5 cycles, long sleepers 6 cycles. Sun/moon symbols show whether the time is during day or night.
4. Set Alarm and Establish Routine
Use the recommended time for your alarm. For best results: Keep times consistent, even on weekends. Your circadian rhythm works best with consistency. After 1-2 weeks of regular use, you should notice improvements in sleep quality and morning alertness. Experiment with different cycle numbers to find your personal optimum.
Practical Use Cases
Optimizing Work Routine
If you need to wake up at 7:00 AM, the timer shows that 11:30 PM, 10:00 PM, or 8:30 PM are ideal bedtimes (5-7 cycles). Instead of simply aiming for "8 hours", synchronize with natural cycles. Many report that 7.5h with cycle timing is more restful than 8h with poor timing.
Shift Work & Variable Times
Shift workers with changing work times can calculate optimal sleep time for each shift. Early shift with alarm at 5:00 AM? Bed at 9:30 PM (5 cycles). Late shift and only home at 2:00 AM? Wake at 10:00 AM (5 cycles from 2:30 AM sleep). The timer adapts flexibly to any situation.
Power Naps & Afternoon Sleep
Use the timer for naps too. A complete cycle (90 min) or a short nap (20 min, before first deep sleep) are ideal. The timer can show: If you fall asleep now (2:00 PM), you wake up refreshed at 3:30 PM. Avoid 30-60 min naps – these often end in the middle of deep sleep and cause sleep inertia (grogginess).
Jetlag Recovery & Travel
After international flights, the timer helps you quickly adapt to new time zones. Plan your first night in the new zone with optimal cycles. Instead of "I must sleep 8h", focus on complete cycles at local time. This significantly accelerates circadian rhythm adjustment.
Fixing Chronic Fatigue
If you wake up exhausted despite "enough sleep", poor cycle timing might be to blame. Waking up in the middle of deep sleep (e.g., after 8h = 5.33 cycles), you feel bad. Try 7.5h (5 cycles) instead – many report that less sleep time with better timing is more restful. The timer helps experiment systematically.
Frequently Asked Questions (FAQ)
What are sleep cycles and why 90 minutes?
A sleep cycle goes through four phases: light sleep (N1, N2), deep sleep (N3), and REM sleep. A complete cycle lasts an average of 90 minutes. Waking during light sleep (between cycles) is easier and more pleasant than waking in the middle of deep sleep, where disorientation and fatigue (sleep inertia) occur. The 90-minute rule is an average – individual cycles vary between 80-110 minutes.
Does this work for everyone?
The 90-minute rule is a scientifically supported average, but individual sleep cycles vary. Some people have 80-minute cycles, others 100-minute. The timer offers a good starting point. Experiment: If 7.5h isn't optimal, try 6h or 9h. After a few weeks of testing, you'll find your personal optimum. More important than perfect cycles is consistency.
Why are 15 minutes added for falling asleep?
15 minutes is the average time people need to fall asleep (sleep onset latency). If you fall asleep faster (good sleep hygiene, exhaustion), it might be 5-10 minutes. With sleep problems, it can be 20-30 minutes. The timer uses 15 min as a compromise. You can adjust mentally: If you should go to bed at 11:00 PM but only need 5 min to fall asleep, you can wait until 11:10 PM.
Is more sleep always better?
No. Quality beats quantity. 7.5h with good cycle timing is better than 8.5h with poor timing. Too much sleep (over 9-10h regularly) can even have negative effects (sluggishness, increased disease risk). Most adults need 7-9h (5-6 cycles). More important than exact hours is that you wake up refreshed. Use the timer to find your personal optimal duration.
What is sleep inertia and how do I avoid it?
Sleep inertia is the groggy, disoriented feeling when waking in the middle of deep sleep. It can take 30-60 minutes until you're fully functional. Cause: Alarm rings during deep sleep phase (typical in the middle of a cycle). Solution: Wake between cycles, during light sleep. The Sleep & Wake Timer helps achieve exactly that – alarm during natural wake-ready phases.
Should I sleep differently on weekends?
For optimal sleep health: No. Consistent times (even on weekends) stabilize your circadian rhythm best. "Social jetlag" (staying up late Friday/Saturday, sleeping late Sunday) disrupts rhythm and makes Monday morning harder. Reality: Many want weekend flexibility. Compromise: Maximum 1-2h deviation. Use the timer for both scenarios – weekday and weekend times – to optimize both.
What about sleep hygiene and environment?
Optimal timing only helps if basics are right: Dark, cool room (61-66°F), no screens 1h before sleep, no caffeine after 2 PM, regular exercise (but not shortly before sleep). The Sleep Timer optimizes timing, but sleep hygiene is a prerequisite. Poor timing with good hygiene is better than good timing with poor hygiene. Ideal: optimize both.
Can I catch up on sleep debt?
Partially. Acute sleep debt (1-2 bad nights) can be compensated with longer sleep – choose 6 cycles (9h) instead of 5. Chronic sleep debt (weeks/months of insufficient sleep) can't simply be "caught up". You need weeks of consistent, sufficient sleep for recovery. The timer helps establish optimal patterns starting now. Prevention is better than repair: Avoid sleep debt through consistent cycle planning.
Are my inputs saved or tracked?
No, absolutely not. The Sleep & Wake Timer works completely locally in your browser. No times are stored on servers, no sleep patterns are analyzed or tracked. Your sleep habits are private. The tool has no backend communication. 100% GDPR compliant and without any tracking or analytics. Your sleep planning remains your business.
Privacy Guarantee
- ✓ All calculations occur completely locally
- ✓ No sleep times are saved or transmitted
- ✓ No tracking of your sleep patterns or habits
- ✓ No server communication, no cookies
- ✓ No analytics or behavioral profiling
- ✓ 100% GDPR/DSGVO compliant by design