What time should I go to bed to wake up at 6:30 AM?
9:15 PM gives 9 hours of sleep in six cycles and 10:45 PM gives 7 h 30 min in five, both counting 15 minutes to fall asleep. 12:15 AM gives 6 hours, under the 7 recommended for adults.
For an alarm at 6:30 AM, the bedtimes that fit whole sleep cycles are 9:15 PM, for 9 hours of sleep, and 10:45 PM, for 7 h 30 min. Both count 15 minutes to fall asleep, and the calculator below already has the alarm set.
Bedtimes, longest night first
A sleep cycle averages about 90 minutes but runs from roughly 70 to 120 depending on the person and the night, so these times are estimates. If you know your own rhythm, the cycle length above can be set to match it.
Counting back from 6:30 AM in 90-minute cycles, then 15 minutes more to fall asleep, gives four bedtimes: 9:15 PM for six cycles, 10:45 PM for five, 12:15 AM for four and 1:45 AM for three. Only the first two reach the 7 hours or more recommended for adults.
The 90 minutes are an average. With 80-minute cycles, five of them would end at 6:30 AM after falling asleep at 11:35 PM instead. The cycle length and the time to fall asleep can both be changed in the calculator.
9:15 PM gives 9 hours of sleep in six cycles and 10:45 PM gives 7 h 30 min in five, both counting 15 minutes to fall asleep. 12:15 AM gives 6 hours, under the 7 recommended for adults.
6 h 15 min, once the 15 minutes to fall asleep are taken out. That is 4 full cycles of 90 minutes and 15 minutes into the next one.
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