REM Sleep Calculator: Ideal Bedtime and Wake-Up Time

The REM Sleep Cycle Calculator

From the ‘80s rock band name to Ariana Grande’s hit beauty line, the term “REM” has become a cultural signifier of dreams and imagination. But it’s more than a symbol. The Rapid Eye Movement stage of sleep is, in fact, when dreaming—and essential memory consolidation—occurs.

Understanding REM sleep and sleep cycles at large can actually help you sleep better and feel more rested. Using our Sleep Cycle Calculator, you can align your bedtime and wake-up time with your natural sleep cycle, making your mornings more manageable. This strategy may prevent sleep inertia, the grogginess and disorientation you experience when you wake up abruptly from REM sleep.

What Is a Sleep Calculator?

A sleep calculator is a tool or chart that tells you the ideal time to fall asleep and wake up. It enhances sleep quality and promotes easy, mental fog-free mornings.

By studying brain activity during sleep and morning cognitive test performance, scientists have determined the ideal window within the sleep cycle to wake up and start your day. Based on this information, a sleep calculator projects what time you should set your alarm given the time you go to bed, or vice versa. We call using this calculator and technique the “Sleep Cycle Strategy.”

What Time Should I Go to Sleep? What Time Should I Wake Up?

For quick reference, we’ve provided our Sleep Cycle Calculator table below. However, we recommend reading the remainder of this guide before using it so you understand how and why it works.

This calculator is intended for adults only. Per Centers for Disease Control and Prevention (CDC) guidelines, we recommend at least 7 hours of sleep each night. However, we know that isn’t always possible and included projections for four sleep cycles (6 hours) in our chart as well.

The table below lists the recommended wake-up time based on what time you you go to sleep and how many hours of rest you need. Four sleep cycles is 6 hours of sleep, five sleep cycles is 7.5 hours, and six sleep cycles is 9 hours.

Note: This table factors in 15 minutes to fall asleep, followed by 90-minute sleep cycles. If you typically take more or less time to fall asleep, add or subtract those minutes from the projected wake-up time.

Understanding the REM Sleep Cycle Calculator

Now that you’ve seen the calculator, you can dive into the theory behind it! As you read, remember that sleep is a complex science and not yet fully understood.

This guide reflects the latest research, but the Sleep Cycle Strategy is not a verified method of improving sleep quality or eliminating sleep inertia. That said, many sleepers have found relief following sleep calculators.

Our Sleep Cycle Strategy guide begins with the essential question: How much sleep do you need?

How Much Sleep Do You Need?

The CDC lays it out simply, using research from the National Sleep Foundation, American Academy of Sleep Medicine, and Sleep Research Society. The CDC provides the following sleep guidelines for a healthy body and mind depending on your age. 

 Source: https://www.cdc.gov/sleep/about_sleep/how_much_sleep.html

The amount of sleep you get dramatically impacts your physical and mental well-being. However, duration isn’t the only factor in the sleep health equation. The Sleep Cycle Strategy prioritizes waking up at ideal intervals along your sleep cycles, so you feel alert and refreshed.

Sleep Cycles

What Are Sleep Cycles?

Sleeping through the night may feel like one continuous session of uniform unconsciousness with a few dreams or interruptions here and there. But sleep is more complicated than you may think.

In a single night, you move through numerous cycles of sleep—typically four to six, depending on how long you’re out. Each cycle comprises four distinct stages, serving unique brain and body maintenance purposes.

A person’s “sleep architecture” refers to their progression through these four stages. Once you fall asleep initially, you’ll go through Stage 1, 2, 3, and REM sleep, then restart the cycle.

How Long Is a Sleep Cycle and How Many Sleep Cycles Do You Need Each Night?

On average, a single sleep cycle lasts 90 minutes. Ideally, you should get five or six sleep cycles a night.

What Are the Stages of Sleep?

You don’t need to understand every physical or neurological facet of sleep’s four stages to implement the REM Sleep Cycle Strategy—just the fundamentals. Below, we’ve compiled a brief overview of what happens in your brain and body during each phase.

Stage 1 (N1)

Duration

• 1-5 minutes
• 5% of total sleep time

Characteristics

• Non-REM (NREM)
• Lightest stage of sleep
• Brain activity: Theta waves (low voltage)

Functions and Occurances

• Body begins to relax
• Breathing, heart rate, and eye movements slow

Stage 2 (N2)

Duration

• About 25 minutes in the first sleep cycle
• Duration increases with each successive cycle
• 45% of total sleep time

Characteristics

• Non-REM (NREM)
• Brain activity: Sleep spindles (powerful neuronal firing bursts) and K-complexes (longest brainwaves)

Functions and Occurances

• Decrease in body temperature
• Eye movement stops
• Become less aware of your surroundings
• Memory consolidation begins
• When bruxism (teeth grinding) may occur

Stage 3 (N3)

Duration

• About 20-40 minutes
• 25% of total sleep time

Characteristics

• Non-REM (NREM)
• Deepest stage of NREM sleep
• Difficult to be woken from, causes sleep inertia (mental fog)
• Brain activity: Delta waves (low voltage, high frequency)

Functions and Occurances

• Complete muscle relaxation
• Lower blood pressure and slower breathing
• Declarative/explicit memory consolidation
• Tissue repair and regrowth, bone and muscle building, immune system strengthened
• When sleepwalking, night terrors, and bedwetting may occur

Stage 4 (REM)

Duration

• About 10 minutes in the first sleep cycle, up to 1 hour in the last
• Duration increases with each successive cycle
• 25% of total sleep time

Characteristics

• REM (Rapid Eye Movement)
• Difficult to be woken from, causes sleep inertia (mental fog)
• Brain activity: Beta waves (High activity, similar to wakefulness)

Functions and Occurances

• Muscle paralysis/muscle atonia
• Fast, irregular breathing and increased pulse
• Rapid eye movement
• Increased brain metabolism
• When dreaming takes place
• Emotions and emotional memories processed and stored
• Supports brain development, learning, problem-solving, and memory

Sources:
https://www.ncbi.nlm.nih.gov/books/NBK526132/ https://www.verywellhealth.com/the-four-stages-of-sleep-2795920

REM Sleep

What Is REM Sleep, and Why Is REM Sleep Important?

Of all the sleep stages, you’ve likely heard the most about REM. The fascination with REM sleep largely stems from its seeming contradictions. During REM, the body is asleep, and all skeletal muscles are atonic, but your brain is highly active. That's why REM is also known as paradoxical or desynchronized sleep.

Throughout REM sleep, the brain does the difficult work of processing and consolidating emotions and memories. As a result, intense dreams occur during this phase, even if you don't remember them.

REM sleep is also essential to learning. As explained by Dr. James B. Maas, professor and former chairman of Cornell University’s psychology department: “The brain busily replenishes neurotransmitters that organize neural networks essential for remembering, learning, performance and problem-solving.”

What Is Sleep Inertia and When Does It Occur?

The key principle of the Sleep Cycle Strategy is avoiding waking up during Stage 3 or REM sleep, which can cause the mental fog of sleep inertia. By nature, it’s more difficult to wake someone from these latter sleep stages. However, the piercing sound of an alarm clock is designed to do just that.

Sleep inertia is the disconnect between your brain and body that occurs if you wake up abruptly from deep or slow-wave sleep. Your body may be awake, but your brain hasn’t quite caught up, lingering in a state of mental fog. And it’s not just a feeling of grogginess—cognitive tests show moderate impaired mental performance for 30 to 60 minutes after waking from Stage 3 deep sleep.

Our Sleep Cycle Calculator tells you when to go to bed and when to set your alarm. Your alarm should go off after you've completed your fifth or sixth sleep cycle and circled back to the beginning. Waking up from the lightest sleep stage, you'll feel more energized and refreshed.

Sleep inertia is the disconnect between your brain and body that occurs if you wake up abruptly from deep or slow-wave sleep.

Final Tips for Following the Sleep Cycle Strategy

There may be complex science behind it, but following the Sleep Cycle Strategy is simple. Using the Sleep Cycle Calculator, choose the bedtime and corresponding wake-up time that works best for your schedule, then build your routines around it.

It'll take time for your mind and body to adjust, but setting a consistent sleep schedule will do wonders for your energy and mood. Even if you have trouble falling asleep at first, stick with it. Eventually, your circadian rhythms will sync up with your new schedule.

You can implement additional sleep hygiene practices to make the transition smoother, like meditating before bed or getting natural sunlight first thing in the morning.

Also, when your alarm goes off in the morning, resist the urge to hit snooze. For this method to work, you need to actually get out of bed and start your day at the scheduled time.

These tips aside, you're ready to hit reset on your sleep and implement the Sleep Cycle Strategy!

Disclaimer: Nolah does not provide medical advice. All resources on the Nolah blog, including this article, are informational only and do not replace professional medical counsel. Talk to your doctor about any health, mental health, or sleep-related issues.