SleepCycleCalcWake Up Calculator
Sometimes bedtime is the fixed point — you know when you are getting into bed, and the question is when to set the alarm. Enter your bedtime and get the wake-up times that complete full 90-minute sleep cycles.
Wake-up times are counted forward from when you fall asleep, in full 90-minute cycles. Aim to wake at the end of a cycle, not in the middle of deep sleep.
Choosing between the wake times
The calculator shows four options, from 3 cycles (4½ hours — emergency territory) to 6 cycles (9 hours). For a normal day, pick by total sleep first and cycle position second: if 5 cycles lands at 6:45 AM and 6 cycles at 8:15 AM, and your morning allows either, the extra cycle is almost always worth more than the earlier start. Cycle timing fine-tunes a sufficient night; it does not rescue an insufficient one.
Weekend lie-ins, handled honestly
Sleeping far past your weekday wake time shifts your body clock later, which is why Monday mornings feel like jet lag ("social jet lag" is the term researchers use). If you want extra weekend sleep, adding one cycle (90 minutes) is a reasonable compromise: real extra rest, without moving your rhythm by half a day. Going to bed earlier on Friday beats sleeping until noon on Sunday for most people.
Frequently asked questions
What time should I wake up if I go to bed at 11 PM?
With a 15-minute fall-asleep buffer, you fall asleep around 11:15 PM. Full-cycle wake times are 3:45 AM (3 cycles), 5:15 AM (4), 6:45 AM (5) and 8:15 AM (6). For a normal morning, 6:45 AM or 8:15 AM are the sensible targets.
Is waking up at 5 AM healthy?
It can be, if the bedtime moves with it. A 5 AM wake-up with 5 full cycles means being in bed by about 9:15 PM. The early wake-up itself is neither virtuous nor harmful — the total sleep and its consistency are what matter.
Why does my alarm feel brutal some days and fine on others?
Often it is cycle position: an alarm in deep sleep feels brutal, the same alarm 20 minutes later in light sleep can feel fine. Shifting bedtime or wake time by half a cycle is a cheap experiment before assuming something is wrong with you.