Sleep Calculator
Best bedtime or wake-up time
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About this calculator
Sleep moves in cycles of roughly 90 minutes. Waking at the end of a cycle usually feels easier than being pulled out of deep sleep. The calculator adds 15 minutes to fall asleep.
The formula
Sleep time = number of cycles × 90 minutes + about 15 minutes to fall asleep
Worked exampleWake at 07:00 → fall asleep around 23:15 (5 cycles) or 21:45 (6 cycles).
Frequently asked questions
How many cycles do I need?
Most adults feel best with 5–6 cycles, about 7.5–9 hours.
Is 90 minutes exact?
No. Cycle length varies between people and through the night.
What if I cannot fall asleep in 15 minutes?
Adjust by shifting the time later or earlier to match your usual routine.
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