Wake-Up Time Calculator

Sleep researchers have found that sleep progresses in roughly 90-minute cycles, each moving through light sleep (N1 and N2), deep slow-wave sleep (N3), and REM sleep stages. Waking at the end of a cycle — rather than in the middle of deep sleep — leaves you feeling alert and refreshed rather than groggy. The calculator first adds your estimated fall-asleep time (the sleep onset latency) to your bedtime to find when sleep cycles actually begin. It then adds 4, 5, or 6 complete 90-minute cycles — equaling 6, 7.5, and 9 hours of actual sleep respectively — to identify the optimal wake-up windows. The default fall-asleep estimate of 14 minutes reflects the average onset latency; adjust this up or down based on your typical experience for more accurate results.