Wake-Up Time Calculator — Best Alarm Times by Sleep Cycles

If going to bed at 11 PM (asleep by 11:15 PM): 4:45 AM (3.5 cycles), 6:15 AM (5 cycles), 7:45 AM (5.5 cycles). Five or six complete cycles is recommended for adults. The key is waking at the END of a cycle, not in the middle of one.

7 hours is better for most adults. However, 6 hours aligned with complete sleep cycles (4 cycles) can feel more restful than 7 hours that interrupt a cycle. Consistently getting under 7 hours is associated with increased risk of obesity, diabetes, and cognitive decline.

You might be waking in the middle of a deep sleep cycle. 8 hours doesn't align perfectly with 90-minute cycles (5 cycles = 7.5h, 6 cycles = 9h). Try 7.5 hours instead and see if you feel more alert. This is the most common reason people feel groggy despite 'enough' sleep.

If you fall asleep by 10:15 PM, the best wake-up times are: 5:45 AM (5 cycles, 7.5 hours), 4:15 AM (4 cycles, 6 hours), or 7:15 AM (6 cycles, 9 hours). For most adults, 5:45 AM gives the ideal 5 complete cycles of sleep.

One complete sleep cycle lasts approximately 90 minutes and includes four stages: light sleep (N1), deeper light sleep (N2), deep sleep (N3), and REM sleep. Early cycles have more deep sleep; later cycles have more REM. This is why sleeping 7.5 hours (5 full cycles) often feels better than 8 hours.