Enter the time you want to wake up or the time you plan to sleep. The calculator suggests ideal bed or wake times aligned to 90-minute sleep cycles.
Sleep runs in roughly 90-minute cycles. The tool counts back or forward in 90-minute blocks (plus time to fall asleep) so you wake between cycles, not mid-cycle.
Waking during deep sleep leaves you groggy. Waking at the end of a cycle, in lighter sleep, tends to feel more refreshing even with the same total hours.
Most adults do best with 5 to 6 complete cycles, about 7.5 to 9 hours. The calculator suggests times that give whole cycles within that range.
← View all Finance & Health CalculatorsBrowse all 1,100+ tools →