Sleep Calculator
Find the best times to sleep and wake up based on natural 90-minute sleep cycles. Calculate optimal bedtimes when you know your wake time, or find ideal wake times when you know your bedtime. Wake feeling refreshed.
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Sleep Cycle Info
Each sleep cycle is approximately 90 minutes. Waking at the end of a cycle helps you feel more refreshed.
Recommended Sleep by Age
For informational purposes only. Consult a healthcare provider for sleep concerns.
All calculations happen in your browser. No data is sent to any server.
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Add this tool to your website with customizable styling
How to Use
- 1 Choose calculation mode — Select whether you want to find bedtimes (if you know when you need to wake up) or wake times (if you know when you're going to bed).
- 2 Enter your time — For bedtime mode, enter when you need to wake up. For wake time mode, enter when you plan to go to bed.
- 3 Adjust fall asleep time — The default is 15 minutes. Adjust this based on how long it typically takes you to fall asleep.
- 4 Click Calculate — Press the Calculate button to see your recommended sleep or wake times.
- 5 Choose your time — Review the options ranging from 3 to 6 sleep cycles. Times marked "Excellent" (5-6 cycles) are optimal for feeling well-rested.
Frequently Asked Questions
How does the sleep calculator work?
The calculator uses 90-minute sleep cycles to determine optimal sleep and wake times. Waking at the end of a complete cycle (rather than in the middle) helps you feel more refreshed and alert. The calculator factors in time to fall asleep (typically 15 minutes) to ensure you complete full cycles.
Why add 15 minutes for falling asleep?
Most people take 10-20 minutes to fall asleep. The calculator adds this buffer so your actual sleep time aligns with complete cycles. You can adjust this based on how quickly you typically fall asleep — if you fall asleep faster, reduce it; if it takes longer, increase it.
How many hours of sleep do I need?
Adults (18-64) typically need 7-9 hours of sleep per night. Teens (14-17) need 8-10 hours, and children (6-13) need 9-11 hours. Individual needs vary based on genetics, activity level, and overall health. Pay attention to how you feel with different amounts of sleep to find your optimal duration.
What makes some times "excellent" vs "fair"?
Excellent times (5-6 cycles, 7.5-9 hours) align with recommended sleep duration for adults. Good times (4-5 cycles) provide adequate rest. Fair times (3-4 cycles, ~6 hours) represent the minimum for adults. Fewer than 3 cycles is not recommended for regular sleep as it can lead to sleep deprivation.