Sleep Cycle Calculator
Enter your desired wake-up time to find the best bedtimes that align with complete 90-minute sleep cycles.
100% client-side · no upload
Suggested bedtimes (includes ~14 min to fall asleep):
How to use
- Enter the time you need to wake up.
- Click Calculate Bedtimes to see six suggested bedtimes.
- Choose a bedtime that gives you 5–6 complete cycles (7.5–9 hours) for full rest.
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Frequently Asked Questions
- Is this sleep cycle calculator free?
- Yes, completely free with no signup and no usage limits.
- Does my data leave my device?
- No. All calculations run in JavaScript inside your browser. Nothing is sent to any server.
- Does it work on mobile?
- Yes. The calculator is mobile-first and works on iPhone Safari and Android Chrome.