Sleep Cycle Calculator

Plan a wake-up or bedtime around 90-minute sleep cycles. A typical sleep cycle lasts about 90 minutes, and waking at the end of a cycle (rather than mid-cycle) feels easier. Add a short buffer for falling asleep (default 15 minutes) and the calculator lists the bedtimes that put you at the end of 3–6 cycles for a chosen wake time, or the wake times for 3–6 cycles if you go to bed now or at a set time. Adjust the cycle length and buffer to match your own rhythm. Everything runs locally in your browser.

Wake time

Cycle length (min)

Fall-asleep buffer (min)

A sleep cycle averages ~90 minutes (it shortens slightly through the night). Most adults need 4–6 cycles (6–9 hours). Waking at a cycle boundary tends to feel less groggy. Suggested times below assume you fall asleep 15 minutes after lights out. The 6-cycle option is marked as the typical adult target. Runs locally.