Sleep Cycle Calculator
Wake up refreshed, not groggy. Time your sleep around your body’s natural 90-minute cycles.
🩺 Built on sleep science by Dr. Khawar, MBBS
What time do you need to wake up?
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Join the waitlist →How does this calculator work?
Sleep happens in cycles of roughly 90 minutes, moving through light sleep, deep sleep, and REM. Waking at the end of a full cycle, rather than the middle of deep sleep, is why you sometimes feel refreshed after less sleep and groggy after more. This tool counts back or forward in 90-minute blocks and adds an average 15 minutes to fall asleep, so your alarm lands at the natural end of a cycle.
How many sleep cycles do I need?
Most adults do best on 5 to 6 complete cycles per night, about 7.5 to 9 hours. Five cycles is the practical minimum for most people. Regularly getting fewer than four builds sleep debt that affects mood, focus, and health over time.
Why does the caffeine cutoff matter?
Caffeine has a half-life of around 5 to 6 hours, meaning half of it is still in your system that long after your last cup. Even if you fall asleep, late caffeine reduces deep sleep quality. The cutoff shown is about 8 hours before bedtime, which clears most caffeine before you sleep.
© SpiritualSleep · Where Sleep Meets Mindfulness
This tool is for general educational purposes and is not medical advice. If you have a persistent sleep problem, please consult your own healthcare provider.