Sleep Calculator

Find your ideal bedtime or wake-up time based on 90-minute sleep cycles. Wake up feeling refreshed.

Last updated: January 2026

Sleep Calculator

Select your preference to see ideal sleep times.
Note: This tool is a screening aid, not a medical assessment. Results do not constitute medical advice. Consult a healthcare provider for health decisions. Full disclaimer

Why sleep cycles matter

Sleep occurs in 90-minute cycles, each consisting of light sleep, deep sleep, and REM sleep. Waking up in the middle of a cycle (especially during deep sleep) causes sleep inertia — that groggy, disoriented feeling. Waking up between cycles leaves you feeling more alert and refreshed.

The average adult needs 5-6 full sleep cycles per night (7.5-9 hours). This calculator works backward from your wake-up time to find bedtimes that end a cycle, or forward from your bedtime to find optimal wake times.

Tips for better sleep

Go to bed and wake up at the same time every day — even on weekends. Avoid screens 1 hour before bed (blue light suppresses melatonin). Keep your bedroom cool (65-68°F / 18-20°C). Avoid caffeine after 2 PM and alcohol before bed. Exercise during the day but not within 2 hours of bedtime.

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