Free Sleep Calculator Online — Find optimal bedtime based on sleep cycles
If you go to sleep right now, you should wake up at:
Sleep Calculator FAQ
How does the sleep calculator work?
It calculates optimal times based on 90-minute sleep cycles plus 15 minutes to fall asleep. Waking between cycles helps you feel refreshed.
How many hours of sleep do I need?
Most adults need 5-6 complete cycles (7.5-9 hours). The calculator shows options for 3-6 cycles.
What is a sleep cycle?
A sleep cycle lasts ~90 minutes and includes light sleep, deep sleep, and REM stages. Waking at the end of a cycle feels more natural.
How to Use Our Sleep Calculator
Enter the time you need to wake up, and the calculator will suggest optimal bedtimes based on 90-minute sleep cycles. Alternatively, enter when you're going to bed to find the best wake-up times.
Waking up between sleep cycles helps you feel more refreshed and less groggy. This tool uses sleep science to recommend times that align with your body's natural rhythm for better rest quality.
Why Use Our Sleep Calculator?
It's free, instant, and based on established sleep science. Get personalized bedtime or wake-up recommendations that account for the average 14 minutes it takes to fall asleep.
What is a sleep cycle?
A sleep cycle lasts approximately 90 minutes and includes light sleep, deep sleep, and REM stages. Most adults need 5-6 complete cycles (7.5-9 hours) per night for optimal health and alertness.
Why do I feel tired after 8 hours of sleep?
You may be waking up in the middle of a deep sleep phase. By timing your alarm to the end of a complete cycle, you wake during lighter sleep and feel significantly more refreshed.
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