Calculate optimal bedtimes and wake-up times based on 90-minute sleep cycles. Wake between cycles and feel energized.
Keep bedroom between 60-67°F (15-19°C). Cooler temperatures promote deeper sleep.
Avoid blue light 1 hour before bed. Use night mode or blue-light glasses.
Stop caffeine 6+ hours before bed. It has a half-life of ~5 hours.
Go to bed and wake up at the same time daily, even on weekends.
The Sleep Calculator finds the best times to go to bed or wake up based on 90-minute sleep cycles, so you wake at the end of a cycle feeling refreshed instead of groggy in the middle of deep sleep.
Sleep happens in roughly 90-minute cycles. The calculator counts backward or forward in 90-minute increments, plus time to fall asleep, to suggest bed or wake times that land at the end of a cycle, when waking feels easiest.
Most adults need 7-9 hours, which is about 5-6 complete sleep cycles. The calculator targets full cycles so you wake refreshed rather than mid-cycle.
Waking in the middle of a deep-sleep stage causes grogginess, known as sleep inertia. Timing your alarm to the end of a cycle — what this tool calculates — helps you avoid it.
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