Calculate the best time to wake up or go to bed based on 90-minute sleep cycles. Wake up feeling refreshed, not groggy. Pure client-side.
Average time from lying down to falling asleep
Sleep cycles typically last about 90 minutes and consist of several stages: light sleep, deep sleep, and REM sleep. Waking up in the middle of a cycle can leave you feeling groggy, while waking up between cycles helps you feel refreshed. This calculator finds the optimal wake-up or bedtime based on these 90-minute cycles, accounting for the average 15 minutes it takes to fall asleep.
A complete sleep cycle typically lasts about 90 minutes and includes stages of light sleep, deep sleep, and REM (rapid eye movement) sleep. Most adults need 4–6 cycles per night (6–9 hours).
On average, it takes 10–20 minutes to fall asleep after lying down. The calculator defaults to 15 minutes, but you can adjust this based on your personal experience.
Waking during deep sleep or REM can cause sleep inertia — that groggy feeling. The calculator helps you wake between cycles when you are in lighter sleep stages.
For most adults, 6 hours (4 cycles) is the minimum recommended. However, many people feel better with 7.5–9 hours (5–6 cycles). Individual needs vary based on age, health, and activity level.