Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles — wake up refreshed, not groggy.
Input
How it works
A night of sleep consists of ~90-minute cycles (light sleep → deep sleep → REM). Waking at the end of a cycle leaves you far more refreshed than being pulled out of deep sleep — even with less total sleep. Adults should aim for 5–6 cycles (7.5–9 hours).
Result
09:15 PM
6 cycles · 9h
recommended
10:45 PM
5 cycles · 7.5h
recommended
12:15 AM
4 cycles · 6h
01:45 AM
3 cycles · 4.5h