Sleep Calculator by Sleep Advisor

Why Your Sleep Cycle Matters

Do you sometimes wake up groggy? Humans experience multiple cycles during sleep, and waking in the middle of the wrong one could cause drowsiness. Therefore, it’s helpful to learn how sleep cycles work so you can avoid interrupting these crucial stages of rest. If you’re feeling lost on where to get started, though, we’re here to help. 

We’ll start with a breakdown on how much rest you need before diving deeper into what happens while you sleep and why quality rest is important. That way, you can learn how to optimize your sleep cycle for your best sleep yet.

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How Much Sleep Do You Really Need?

In the US alone, one in ten adults [1] say they’re unable to get sufficient rest every night. Before we cover the stages of sleep, it’s helpful to first discuss how much sleep you should be aiming for each night. Also keep in mind that as we grow older, our sleep needs change.

Kids

While specific ages may require slightly more rest, kids in general need more hours of sleep [2] than any other age group. 

• Newborns: 14-17 hours
• Infants: 12-16 hours
• Toddlers: 11-14 hours
• Kids 5 and up: 9-13  hours

Teens

Teens need less sleep than kids, but still more than adults. Just like with kids, proper rest is crucial for teens’ learning, development, and growth.

• Pre-teens (9-12): 9-12 hours
• Teens: 8-10 hours

Adults

By the time you’re an adult, the amount of sleep you need starts to decrease. This amount fluctuates as you grow older, with seniors needing less sleep than young adults.

• Young adults: 7+ hours
• Adults: 7-9 hours
• Seniors (65+): 7-8 hours

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Stages of Sleep

There are four stages of sleep [3] which are divided into two phases: rapid eye movement (REM) and non-rapid eye movement (non-REM). The first three stages involve non-REM sleep, while the fourth and final stage is REM sleep. 

During a sleep cycle, you will move through each of these four stages, starting with Stage 1 (non-REM slumber) and ending with REM. In order to complete one full sleep cycle, you must pass through all four stages. Once you are done with your final sleep stage — REM — you then move on to another sleep cycle, repeating this pattern throughout the night until you rise in the morning. 

Each cycle lasts for about 90 to 110 minutes.

What Happens During Each Stage of Sleep 

Phase 1

Stage 1 is a light rest that lasts roughly 5 to 10 minutes. During this time, your eye movement slows, and your muscles start relaxing. You may also experience hypnic jerking, aka a sudden muscle contraction. 

Stage 2 is when your brain waves and heart rate slow down, body temperature drops, and eye movement ceases. The second stage typically lasts 10 to 25 [4] minutes.

Stage 3 is when you succumb to a deep slumber, and you’re likely to feel disoriented if awakened. During this stage, which lasts anywhere from 20 to 40 [5] minutes,  you generate very slow brain waves, which is why this stage is also known as slow-wave. You also have no eye or muscle movement.

Phase 2

Stage 4 is the most important stage because it’s where REM sleep occurs. 

REM, is when your brain waves begin to quicken again as you leave deep sleep. Your heart rate and blood pressure also start to rise, and your breathing becomes more rapid. 

As the name suggests, this stage is marked by faster eye movements (aka rapid eye movement). Most of your dreaming takes place during REM sleep. To avoid physically acting out these dreams, though, your legs and arms remain in a state of paralysis. According to the American Psychological Association [6], REM sleep is highly important because it “replenishes neurotransmitters that organize neural networks essential for remembering, learning, performance and problem solving.”

As you cycle through multiple REM stages during the night, know that the first few only last around 10 minutes before getting increasingly longer. The amount of REM slumber you need also depends on your age. For example, babies and young children need the most, but as you grow older and move into adolescence and adulthood this amount decreases.

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The Effects of Sleep Deprivation

A bad night’s rest does more damage than you think. Beyond making you feel downright cranky, consecutive nights of poor rest can significantly interfere with your physical and mental health. 

Sleep deprivation puts you at risk for chronic health problems [7] such as heart disease, high blood pressure, diabetes, and kidney disease. Poor rest makes it harder for your body to fight off illness, weakening your immune system and exposing you to sickness. Your energy levels are down, and you may experience signs of premature aging.

The mental effects [8] are just as daunting. Insufficient rest can lead to depression, anxiety, emotional dysregulation, and poor cognitive functioning.

Chronic insomnia can also increase your risk of injury — not just for yourself but for the people around you. Drowsy driving results in car crashes, while older adults are more prone to accidents and falls that may cause broken bones.
However, don’t let these statistics keep you up at night. Most of these effects are a result of long-term sleep deprivation, but it’s still helpful to recognize these pitfalls so you can understand why it’s so crucial to prioritize quality rest. Remember that it’s relatively normal for most of us to experience a bad night of sleep every now and then. By optimizing your sleep cycle for your personal routine and schedule, you can enjoy better sleep and a greater quality of life overall.

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Sleep Hygiene Tips for Quality Rest

If you feel like your sleep quality is subpar, don’t be alarmed. Luckily, there are plenty of strategies for promoting better rest .

1. Maintain a consistent bedtime and wake-up time, including weekends. You can use this calculator to help determine your ideal schedule and then stick to that going forward. 
2. Avoid alcohol, caffeine, and nicotine in the hours close to bedtime as they can disrupt your rest. 
3. Try to refrain from undereating or overeating close to bedtime as going to bed full or hungry can affect your sleep. 
4. If you take naps, don’t doze off too late in the day or for more than 30 minutes as this can make it harder to fall and stay asleep later on. 
5. Physical activity may also help you rest better, so consider going out for a run or walk if you need an afternoon recharge. 
6. Make sure your bedroom is conducive to quality rest by keeping it cool, quiet, and dark. 
7. Stress can keep you up at night. Help quell any anxiety by establishing a nightly routine before bed, such as reading a book or drinking hot tea. This can help relax you prior to falling asleep.

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Last Word of Advice

If you want to wake up more refreshed, this sleep calculator could be the solution of your dreams. Remember that as you rest, you move through four stages which make up a full cycle of sleep. Experts recommend waking during the first and lightest stage after completing 5 to 6 full sleep cycles (or 7 to 9 hours of rest). By using our sleep calculator, you can determine how to optimize your sleep cycle. Once you’re an expert on your individual rhythm, you can achieve better quality rest in a shorter amount of time. 

This knowledge, combined with healthy sleep habits, can improve your slumber. Your doctor (and those around you) are sure to offer many thanks for prioritizing your sleep. 

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Popular Questions

How many hours of sleep is recommended?

Although the calculator can help you wake up during a lighter slumber, that’s not to say you should actively pursue fewer hours of sleep than recommended by the medical community. Experts suggest that adults get between 7 and 9 [9] hours of sleep each night, which correlates to 5 or 6 full cycles. 

However, this amount can vary depending on your health and personal circumstances. For instance, if you are recovering from a cold, you will likely doze off longer than you would normally. Babies, children, and teens should get even more sleep. For example, a newborn baby needs between 14 and 17 hours of shuteye.

Is it normal to still feel tired after sleeping for 8 hours?

Yes, you can sleep for 8 hours and still feel tired. Even though you got the amount of rest that health experts recommend, you likely woke up toward the end of a sleep cycle. The length of these cycles can vary. 

We mentioned earlier that a complete cycle could last anywhere from 90 to 110 minutes. The duration of each stage can vary too, which further affects the cycle duration. However, each person is different, so you cannot calculate your individual sleep cycle to the exact minute. Instead, these numbers represent a general observation from health experts to help people better understand how we rest.

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References:

1. American Sleep Apnea Association. The State of Sleep Health in America in 2022. Last modified 2022. sleephealth.org/sleep-health/the-state-of-sleephealth-in-america/
2. Nemours KidsHealth. Kids and Sleep. Last modified January 2021. kidshealth.org/en/parents/sleep.html
3. Cleveland Clinic. Sleep Basics. Last modified December 7, 2020. my.clevelandclinic.org.
4. Harvard Medical School. Natural Patterns of Sleep. Last modified December 18, 2007. Healthysleep.med.harvard.edu
5. Kaiser Permanente. Stages of Sleep. Last Modified March 1, 2022. healthy.kaiserpermanente.org/health-wellness/health-encyclopedia/he.stages-of-sleep.hw48331
6. American Psychological Association. Strengthen Your Brain by Resting It. Last modified August 2004. apa.org/monitor/julaug04/strengthen
7. National Heart, Lung, and Blood Institute. What Are Sleep Deprivation and Deficiency? Last modified March 24, 2022. nhlbi.nih.gov/health/sleep-deprivation
8. Columbia Psychiatry. How Sleep Deprivation Impacts Mental Health. Last modified March 16, 2022. columbiapsychiatry.org/news/how-sleep-deprivation-affects-your-mental-health
9. Cleveland Clinic. How Much Sleep Do I Need?. Last modified February 25, 2021. health.clevelandclinic.org.