Calculate the best times to wake up or go to sleep based on 90-minute sleep cycles.
Choose whether you are planning a bedtime or wake-up time, enter the target time, then compare the suggested sleep-cycle options.
Sleep cycles vary in length and the calculator cannot know when you actually fall asleep.
This tool works backwards or forwards in repeated sleep-cycle blocks to produce several possible bedtimes or wake-up times. The options are useful for planning, but they do not measure your personal sleep stages. Real sleep cycles vary between people and across the same night.
A calculated bedtime is not the same as the moment sleep begins. If you usually need 10, 20 or 30 minutes to settle, allow for that before the suggested sleep time. Noise, light, alcohol, caffeine, stress, illness and sleep disorders can also affect sleep quality even when total time in bed looks adequate. The calculator is best used to compare schedules and protect enough sleep opportunity, not to promise that waking at the end of a calculated cycle will prevent tiredness.