What time should I go to bed if I wake up at 6?

Subtract 5 cycles plus a 15-minute buffer: 6:00 AM minus 7 hours 45 minutes is 10:15 PM. For 6 cycles: 6:00 AM minus 9 hours 15 minutes is 8:45 PM. So 10:15 PM or 8:45 PM.

How do you calculate bedtime from wake time?

Take your wake-up time, subtract 5 or 6 full 90-minute cycles, then subtract about 15 minutes for falling asleep. Five cycles plus buffer is 7 hours 45 minutes; six cycles plus buffer is 9 hours 15 minutes.

Is 10 PM a good bedtime?

It depends on your alarm. 10:00 PM plus a 15-minute buffer and 5 cycles (7.5 hours) wakes you at 5:45 AM; with 6 cycles (9 hours) it wakes you at 7:15 AM. Match the bedtime to your alarm using the formula rather than picking a clock time alone.

What is the 90-minute rule for bedtime?

The 90-minute rule says sleep moves in roughly 90-minute cycles, so your time in bed should be a multiple of 90 minutes plus a 15-minute fall-asleep buffer. That gives 7 hours 45 minutes (5 cycles) or 9 hours 15 minutes (6 cycles) in bed.

Should bedtime be the same every night?

Yes. A consistent bedtime trains your circadian rhythm and makes both falling asleep and waking up easier. Keep weekends within about an hour of your weekday bedtime to avoid the drag of a shifting schedule.

What Time Should I Go to Bed? Bedtimes for Any Wake-Up Time

If your alarm is fixed, your bedtime is the variable. Subtract 5 or 6 full 90-minute sleep cycles, plus a 15-minute buffer to fall asleep, from your wake-up time. Here is the math and a table for the most common alarms.

Subtract 5 or 6 full 90-minute cycles plus a 15-minute fall-asleep buffer from your wake-up time. Wake at 6:30 AM means going to bed at 10:45 PM (5 cycles, 7.5 hours) or 9:15 PM (6 cycles, 9 hours).

The formula

Bedtime equals wake-up time, minus a whole number of 90-minute cycles, minus about 15 minutes to fall asleep. Five cycles is 7.5 hours of sleep; six cycles is 9 hours. Subtract the total from your alarm and you get two candidate bedtimes.

Counting backward from the alarm, rather than guessing a bedtime, is the whole trick. It guarantees the hours in bed land as whole cycles instead of ending mid-cycle.

Worked example: wake at 6:30 AM

Start with 6:30 AM. For 5 cycles: 5 times 90 minutes is 450 minutes (7 hours 30 minutes), plus the 15-minute buffer, for a total of 7 hours 45 minutes. 6:30 AM minus 7 hours 45 minutes is 10:45 PM.

For 6 cycles: 6 times 90 minutes is 540 minutes (9 hours), plus 15 minutes, for a total of 9 hours 15 minutes. 6:30 AM minus 9 hours 15 minutes is 9:15 PM. So a 6:30 alarm gives two bedtimes: 10:45 PM or 9:15 PM.

More wake-up times, worked the same way

Wake at 5:30 AM: minus 7 hours 45 minutes is 9:45 PM; minus 9 hours 15 minutes is 8:15 PM. Options: 9:45 PM or 8:15 PM.

Wake at 7:00 AM: minus 7 hours 45 minutes is 11:15 PM; minus 9 hours 15 minutes is 9:45 PM. Options: 11:15 PM or 9:45 PM.

Wake at 8:00 AM: minus 7 hours 45 minutes is 12:15 AM; minus 9 hours 15 minutes is 10:45 PM. Options: 12:15 AM or 10:45 PM.

Notice the pattern: moving your alarm one hour later moves both bedtime options one hour later. Once you know your pair, the schedule scales.

Why the 15-minute buffer belongs in the math

Most people take around 15 minutes to fall asleep, and cycles are counted from sleep onset, not from lights-out. Skipping the buffer means your first cycle starts late and your alarm lands 15 minutes into what should have been a between-cycle wake. If you typically lie awake longer, use 20 or 30 minutes; the formula works the same.

Bedtime also means lights out, screens off, in bed. Scrolling for 40 minutes after your "bedtime" silently deletes half a cycle from the plan.

Which option should you pick?

Choose based on how much sleep you need. Most adults do well on 5 cycles (7.5 hours); people who train hard, are recovering from illness, or simply feel better on more sleep should take the 6-cycle option (9 hours). If you are unsure, try the 5-cycle bedtime for a week: if you wake before the alarm feeling clear, it is enough; if you sleep through it groggy, move to 6 cycles.

Teenagers should default to the 6-cycle option or later bedtimes overall, since ages 13 to 17 need 8 to 10 hours.

Keep the bedtime consistent

The same bedtime every night, weekends included, trains your circadian rhythm to start winding down on schedule. A bedtime that swings by two hours between weeknights and weekends creates the same drag as jet lag. Protect the bedtime the way you protect the alarm: it is the other half of the same appointment.

Run your exact wake-up time

A bedtime calculator takes any alarm time and returns both bedtime options instantly, with the fall-asleep buffer included, so you do not have to do the subtraction by hand.

What Time Should You Go to Bed?