Sleep calculator
Wake up feeling
rested, not groggy.
Your sleep cycle calculator. Find the perfect bedtime or alarm time based on your natural 90‑minute sleep cycles — and stop waking up mid‑cycle.
Chronotype quiz
What's your sleep type?
Answer four questions to find your chronotype — the biological sleep pattern you were born with.
1.On a free day with no alarm, when do you naturally wake up?
2.When do you feel mentally sharpest?
3.If you had to wake up at 6am, how hard is that?
4.When do you naturally feel sleepy at night?
How sleep cycles work
Sleep naturally progresses through 90-minute cycles, each moving from light sleep through deep (slow-wave) sleep and into REM. Waking mid-cycle — when an alarm cuts into deep sleep — triggers sleep inertia: the heavy, disoriented grogginess that can linger for hours. This sleep calculator works backward from your target wake time (or forward from your bedtime) to identify times that land at the end of a full cycle, when your body is closest to waking naturally. Most adults function best on 5 complete cycles (7.5 hours), though individual needs vary between 4 and 6 depending on age, health, and chronotype.