Sleep Calculator
Wake Up Naturally
Improve your sleep cycle with a sunrise alarm clock that simulates dawn light, plays white-noise sounds, and helps you wake up refreshed.
Shop Vivilumens Sunrise Alarm ClockAbout Sleep Calculator
The Sleep Calculator estimates your ideal bedtime or wake-up time based on natural 90-minute sleep cycles. It assumes it takes around 15 minutes to fall asleep and helps you wake up at the end of a cycle — when your body is naturally more alert.
How to use this sleep calculator
- Choose whether you know your wake-up time or bedtime.
- Enter your time and optional sleep latency (default 15 minutes).
- Press Calculate to see recommended times for 3–6 complete sleep cycles.
Understanding sleep cycles
A typical sleep cycle lasts around 90 minutes and includes stages of light, deep, and REM sleep. Waking up in the middle of deep sleep can cause grogginess — called sleep inertia — while waking near the end of a cycle usually makes you feel refreshed.
Tips for better sleep
- Aim for 5–6 full cycles (7.5–9 hours) for best performance.
- Keep consistent sleep and wake times, even on weekends.
- Limit caffeine and screen exposure before bedtime.
- Use your results to plan sleep around your schedule — not just total hours, but timing quality.
FAQ
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What time should I go to sleep to wake up refreshed?
Aim to wake at the end of a 90-minute cycle. From your target wake-up time, count back 5–6 cycles (7.5–9 h) plus ~15 min to fall asleep. -
Are sleep cycles always 90 minutes?
They vary by person and night (~70–110 min). The 90-minute rule is a practical average; adjust based on how you feel on waking. -
Do I really need 8 hours?
Many adults feel best with 5–6 full cycles (7.5–9 h). Teens and athletes may need more; sleep quality and consistency matter as much as total time. -
Does it take exactly 15 minutes to fall asleep?
No—sleep latency differs (5–30+ min). If you usually fall asleep faster/slower, change the latency setting for more accurate schedules. -
Are naps helpful?
Short naps (10–20 min) can boost alertness; a full-cycle nap (~90 min) helps if you’re very sleep-deprived. Avoid napping too late to protect night sleep. -
How do screens, caffeine, and alcohol affect sleep?
Blue light delays melatonin; caffeine can disrupt sleep for 6–8 h; alcohol fragments sleep and REM. Dim screens and limit intake before bed.
Disclaimer
The tools provided on this site are intended for educational and informational purposes only and are not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified health provider with any questions you may have about a medical condition. If you think you may have a medical emergency, call your local emergency number immediately.
Always consult your doctor if you have persistent sleep issues or suspect a sleep disorder such as insomnia or sleep apnea.