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Sleep Calculator
Free online Sleep tool. Fast, accurate, and easy-to-use converter and utility for everyday calculations.
Sleep Calculator
Based on 90-minute sleep cycles and 15 minutes to fall asleep.
Go to bed at:
9:15 PM
6 cycles · 9.0 hours
10:45 PM
5 cycles · 7.5 hours
12:15 AM
4 cycles · 6.0 hours
1:45 AM
3 cycles · 4.5 hours
Sleep Calculator — Best Bedtime & Wake-Up Times
The sleep calculator recommends optimal bedtimes or wake-up times based on 90-minute sleep cycles. Sleeping through complete cycles (4–6 cycles = 6–9 hours) helps you wake up feeling refreshed, while waking mid-cycle causes grogginess. Use this tool to plan your perfect sleep schedule.
Step-by-Step Guide
- 1Choose whether you want to know what time to sleep or what time to wake up.
- 2Enter your desired wake-up time or bedtime.
- 3The calculator accounts for ~15 minutes to fall asleep.
- 4Choose from recommended times that complete 4, 5, or 6 full sleep cycles.
Why Use Our Sleep Calculator?
- Instant browser-side calculation
- 100% private — no data stored
- Visual charts & breakdowns
- Free forever — no sign-up needed
Frequently Asked Questions
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