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Sleep Calculator
Calculate the best times to go to sleep or wake up based on natural 90-minute sleep cycles. Wake up feeling refreshed, not groggy.
Frequently Asked Questions
A sleep cycle lasts approximately 90 minutes and includes both light sleep, deep sleep, and REM (dream) sleep. Most adults need 4–6 full cycles (6–9 hours) per night for optimal rest.
Waking mid-cycle — during deep sleep — causes sleep inertia (grogginess). Waking at the end of a 90-minute cycle, when sleep is lightest, feels much more natural and alert.
On average, it takes about 14 minutes to fall asleep. Our calculator adds a 15-minute buffer to account for this, giving you realistic bedtime recommendations.