Sleep Cycle Calculator | Bedtime and Wake-Up Times

Calculate suggested bedtime or wake-up times using 90-minute sleep cycles and a selected target time.

Calculation Mode

Target Time

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Suggested Sleep Times

To wake up at this time, consider falling asleep at one of these times:

Plan Bedtime Around Sleep Cycles

Choose a wake-up time or bedtime to calculate suggested sleep times based on 90-minute sleep cycles.

Add Time for Falling Asleep

The calculator works with cycle timing, but real sleep depends on how long it takes to fall asleep, sleep quality, caffeine, stress, and room conditions.

Questions People Ask

What is a sleep cycle?

A sleep cycle is approximately 90 minutes and includes light sleep, deep sleep, and REM sleep stages. Most adults complete 4 to 6 cycles per night.

Why do I feel groggy even after 8 hours of sleep?

Waking in the middle of a deep sleep stage causes sleep inertia, that heavy groggy feeling. Waking at the end of a cycle avoids this even with fewer total hours.

How long does it take to fall asleep?

The calculator adds 15 minutes to your bedtime as an average time to fall asleep. Adjust this if you typically fall asleep faster or slower.

What This Tool Does

Sleep Cycle Calculator suggests the best times to wake up or go to sleep based on 90-minute sleep cycle intervals. Waking at the end of a cycle rather than mid-cycle reduces grogginess and morning fatigue.

Typical Use Cases

Use this when setting a wake-up alarm and you want to feel as rested as possible, when adjusting your sleep schedule for a morning commitment, or when trying to improve sleep quality by aligning with natural cycles.

How to Get Your Result

Enter the time you plan to go to sleep.
Click Calculate to see the recommended wake-up times at 4, 5, and 6 cycle intervals.
Choose the alarm time that best fits your schedule.

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