Sleep Calculator
Sleep runs in cycles of about 90 minutes. Enter when you wake up to get two bedtimes that let you wake between cycles, with time to fall asleep included.
How we got it
Wake-up time minus 6 cycles (9 hours) or 5 cycles (7.5 hours) of 90 minutes, minus about 15 minutes to fall asleep. Cycle length varies from person to person, so treat these as a starting point.
Updated . Sources: Hirshkowitz and others, 2015, National Sleep Foundation sleep duration recommendations.
Questions
How many hours of sleep do adults need?
Seven hours or more a night is the common recommendation for adults.
Why wake between cycles?
Waking from deep sleep can leave you groggy. Aiming for the end of a cycle often feels easier.