xCalculator xCalculator
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Go to bed at one of these times:

💡 How sleep cycles work

Each sleep cycle lasts ~90 minutes. Waking up at the end of a complete cycle helps you feel refreshed. The average adult needs 5-6 cycles (7.5-9 hours) per night.

What Is a Sleep Cycle Calculator?

A sleep cycle calculator helps you determine the optimal bedtime or wake time based on the science of sleep architecture. Each sleep cycle lasts approximately 90 minutes, consisting of light sleep, deep sleep, and REM (rapid eye movement) stages. Waking up at the end of a complete cycle—rather than in the middle of one—helps you feel refreshed and alert. This calculator works in two modes: enter your desired wake time to find optimal bedtimes, or enter your bedtime to find the best times to wake up.

When Should You Use This Calculator?

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Early Morning Commitments

Find the best bedtime when you must wake up early for work, travel, or appointments

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Improving Sleep Quality

Stop waking up groggy by aligning your sleep with natural cycle completion

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Shift Work Adjustments

Plan sleep around irregular schedules to maximize rest quality

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New Parent Scheduling

Maximize your limited sleep windows when caring for a newborn

How to Use the Sleep Calculator

  1. 1

    Choose your calculation mode: "Wake up at" or "Go to bed at"

  2. 2

    Enter your target time using the time picker

  3. 3

    Review the suggested times ranked by sleep quality (Best/Good/Minimum)

  4. 4

    Aim for 5-6 cycles (7.5-9 hours) for optimal health and alertness

Frequently Asked Questions

How long is a sleep cycle?
A typical sleep cycle lasts about 90 minutes. During each cycle, your brain progresses through stages: N1 (light sleep), N2, N3 (deep sleep), and REM. The composition of stages changes throughout the night, with more deep sleep early on and more REM in later cycles.
How many sleep cycles do I need per night?
Most adults need 5-6 complete sleep cycles per night, which equals 7.5-9 hours of sleep. Teenagers may need up to 7 cycles, while older adults might function well on 4-5 cycles. Quality matters as much as quantity.
Why do I wake up tired even after 8 hours of sleep?
Waking up during deep sleep (Stage N3) causes sleep inertia—that groggy, disoriented feeling. Using this calculator to wake at the end of a cycle helps avoid deep sleep interruption. Other factors include sleep apnea, alcohol before bed, or inconsistent sleep schedules.
What is the best time to go to sleep?
The best bedtime depends on your wake time and chronotype (natural sleep preference). Most people's bodies naturally release melatonin between 9-10 PM, making this an ideal window. The key is consistency—going to bed at the same time nightly is more important than the exact hour.
Is 6 hours of sleep enough?
Six hours (4 sleep cycles) is the minimum for most adults and not optimal long-term. Chronic short sleep is linked to impaired cognition, weakened immunity, and increased disease risk. If you must sleep only 6 hours, ensure you wake at the end of a complete cycle.
How accurate is the 90-minute sleep cycle?
Sleep cycles typically range from 80-120 minutes, with 90 minutes being the average. Individual variation exists—track your sleep with a wearable device to find your personal cycle length. This calculator provides a solid starting point for most people.
Does this work for naps?
For naps, aim for either 20 minutes (power nap, stay in light sleep) or a full 90-minute cycle. Waking after 45-60 minutes often causes grogginess because you're in deep sleep. This calculator is designed for full night sleep, but the cycle principle applies to naps too.
What factors affect sleep cycle quality?
Alcohol, caffeine, late meals, irregular schedules, and blue light exposure before bed all disrupt sleep architecture. Temperature, noise, and stress also impact cycle quality. For best results, combine this timing calculator with good sleep hygiene practices.