Loona Calculators
Waking up mid-cycle is what makes mornings feel brutal. Sleep runs in cycles of about 90 minutes, so this calculator counts backwards (or forwards) in full cycles and adds about 14 minutes to fall asleep — giving you bedtimes and wake-up times that work with your biology.
A full human sleep cycle — light sleep, deep sleep and dreaming (REM) — averages about 90 minutes. Waking at a cycle boundary, between dreams, feels markedly easier.
Most adults do best with 5 or 6 full cycles — 7 hours 30 minutes to 9 hours. Four cycles (6 hours) is a short-night fallback, not a routine.
It is the average time people take to fall asleep, and yes — without it the cycles end 14 minutes before your alarm. If you fall asleep much faster or slower, shift the suggested times by the difference.