What Time Should I Wake Up or Go to Sleep?
Calculate optimal wake and sleep times based on 90-minute sleep cycles. Wake up refreshed instead of groggy.
Sleep Cycles Explained
Sleep occurs in 90-minute cycles through stages: light sleep → deep sleep → REM (dreaming). A full night has 4-6 complete cycles. Waking up during deep sleep (mid-cycle) causes sleep inertia — that groggy, disoriented feeling. Waking at the end of a cycle (between cycles) feels refreshed and alert. This calculator times your bedtime so you wake between cycles.
How Much Sleep You Need
Adults (18-64): 7-9 hours (5-6 cycles). Teenagers: 8-10 hours. Children (6-13): 9-11 hours. Older adults (65+): 7-8 hours. Consistently getting fewer than 6 hours increases risk of heart disease, obesity, diabetes, and cognitive decline. The CDC considers insufficient sleep a public health epidemic — 1 in 3 American adults doesn't get enough.
The single best sleep improvement most people can make: consistent timing. Going to bed and waking up at the same time every day (including weekends) regulates your circadian rhythm more than any supplement, app, or mattress. Irregular sleep schedules are equivalent to constant mild jet lag.
