Sleep Calculator
Calculate optimal bedtime or wake time
How to Use
Choose calculation mode
Select Sleep Now, By Wake Time, or By Bedtime.
Enter time
If needed, enter your target wake time or bedtime.
Adjust fall-asleep time
Set how long it typically takes you to fall asleep.
View recommendations
See optimal times based on 90-minute sleep cycles, with recommended options highlighted.
Frequently Asked Questions
What is a sleep cycle?
A sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM stages. Most adults need 5-6 complete cycles (7.5-9 hours).
Why is waking between cycles better?
Waking during deep sleep causes grogginess (sleep inertia). Waking at the end of a cycle, during lighter sleep, helps you feel more refreshed.
How long does it take to fall asleep?
Average is 10-20 minutes. If you fall asleep instantly, you might be sleep-deprived. If it takes over 30 minutes, you might be going to bed too early.
Is 6 hours of sleep enough?
For most adults, 6 hours (4 cycles) is the minimum, but 7.5-9 hours (5-6 cycles) is recommended for optimal health and cognitive function.
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