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REM Sleep Calculator

Created by Davide Borchia
Reviewed by Steven Wooding
Based on research by
Hirshkowitz M, Whiton K, Albert SM, Alessi C, Bruni O, DonCarlos L, Hazen N, Herman J, Katz ES, Kheirandish-Gozal L, Neubauer DN, O'Donnell AE, Ohayon M, Peever J, Rawding R, Sachdeva RC, Setters B, Vitiello MV, Ware JC, Adams Hillard PJ. National Sleep Foundation's sleep time duration recommendations: methodology and results summary.; Sleep Health; March 2015See 1 more source
Shen, X., Wu, Y. & Zhang, D. Nighttime sleep duration, 24-hour sleep duration and risk of all-cause mortality among adults: a meta-analysis of prospective cohort studies; Scientific Reports; February 2016
Last updated: Jan 18, 2024

Can you calculate REM sleep? What is the science behind your nightly sleep? Discover it with Omni's tool. Keep reading this article to find out:

  • What is REM sleep?
  • Can you calculate REM sleep hours?
  • How to calculate REM sleep in a cycle.

And much more. Use the REM sleep calculator to improve your knowledge about sleep and the science of dreams!

What is REM sleep?

REM, the acronym for rapid eye movement is a phase of a sleep cycle characterized by physiological changes and modifications in the pattern of brain activity.

REM sleep occurs regularly during sleep, appearing at the end of a sleep cycle. The duration of the REM portion of a cycle varies, becoming longer as the night progresses. During REM sleep, the muscle tone decreases (you go limp), and your body is subjected to drastic changes in the chemical processes in the brain and body. Among them are:

  • Absence of serotonin, norepinephrine, and histamine. These three neurotransmitters regulate the loss of tone and influence the creation of memories and experience of emotions during the REM phase.

  • Peak in acetylcholine. This also causes the loss of muscular tone.

Brain activity also changes drastically: the EEG of a brain during sleep shows activity that closely resembles the one of wakefulness (this is why REM sleep can also be called paradoxical sleep). Neurons fire with the same intensity as when we are awake but show a generalized decrease in coherence, a fact sometimes associated with the experience of dreaming.

How can't we talk about REM sleep without spending some words on rapid eye movement? There is no accepted explanation for this phenomenon. Some hypotheses associated it with the process of handling memories, others with a recreation of the vision process during dreams.

Can you calculate REM sleep?

Not exactly: there is no exact model for the duration and the occurrence of REM sleep during a sleep cycle. The closest approximation we have is to define the end of the REM phase.

Why may you want to know how to calculate a sleep cycle's REM phase? Because you may wish to remember your dreams. Science tells us that focusing on our dream, without distraction as soon as we wake up is the best way to remember our dreams. Since the REM phase occurs at the end of each sleep cycle, waking up at those times may help you recollect your dreams better.

However, breaking your sleep to note your dreamy experiences is not advisable. Limit yourself to recording the ones right after your wake-up time: the increased length of the REM phase will also give you more material!

Let's discover how we can find the times of the ends of each REM phase in your sleep.

  1. Decide the time you will go to sleep.

  2. Choose the time you need before falling asleep.

  3. Sum those quantities: this will be our starting point.

  4. Choose how many sleep cycles you want to sleep:

    • A healthy sleep consists of five sleep cycles.

    • If you are a short-sleeper, select four cycles.

    • If you are a long-sleeper, select six cycles.

  5. Our calculator will show you the time corresponding to the approximate ends of the sleep cycles. To calculate them, we simply incrementally added 90 minutes to the starting time of your sleep.

Waking up around those times maximizes the likelihood of waking during the increased awareness period at the end of the cycle, right after the end of the REM phase. In the early morning, when the REM phase is longer, you may even vividly remember the night's dreams.

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In which part of the night is there REM sleep?

You experience multiple REM sleep phases during the night. These phases happen at the end of the 90-minute cycles that define human sleep, after a longer period of light sleep, with low brain activity.

During REM sleep, your brain fires with increased activity, alongside many physiological and chemical changes in your body.

As soon as the REM phase ends, you wake up for a brief period of time but rarely recollect this moment, as your brain soon returns to sleep.

How can I remember my dreams?

To remember your dreams, you should wake up around the end of a REM sleep phase. Since dreams (the most vivid ones) happen during this phase, when the activity of your brain peaks during the night, waking up right after it maximizes the likelihood of retaining the dreams just experienced.

Try not to get any distractions, and note down the details of your dreams as soon as you open your eyes to avoid covering the memories with the day's events.

When are the REM phases if I go to sleep at 11 PM?

Assuming a sleep night consisting of five sleep cycles, you would experience five REM phases of increasing duration. While it's impossible to define the starting time of these phases, we can approximate the ending times:

  • The first phase ends at 0:30 AM;
  • The second phase ends at 2:00 AM;
  • The third phase ends at 3:30 AM;
  • The fourth phase ends at 5:00 AM; and
  • The fifth and last phase ends at 6:30 AM.

Waking around half past six maximizes the likelihood of remembering your dreams!

Davide Borchia
What time should I go to sleep?
Sleep time
11:00 PM
Time to fall asleep
Number of cycles
REM tends to happen at the end of each sleep cycle:
Sleep cycle number 1 ends at 0:45.
Sleep cycle number 2 ends at 2:15.
Sleep cycle number 3 ends at 3:45.
Sleep cycle number 4 ends at 5:15.
Sleep cycle number 5 ends at 6:45.
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