Sleep Calculator by Age: How Much Sleep You Need at Every Age

Sleep is not a one-size-fits-all affair. A newborn sleeps up to 17 hours a day, a teenager struggles to get 8, and a 70-year-old may wake naturally after 6. Your age is the single biggest predictor of how much sleep your body requires, because the biological role of sleep shifts dramatically across the lifespan. This guide breaks down sleep needs for every age group — from the first week of life to the retirement years — and explains the science behind why those needs change. Use our sleep by age calculator to get personalized recommendations based on your specific age.

Why Sleep Needs Change with Age

Sleep serves different biological purposes at different life stages. In infancy and early childhood, the brain is building neural connections at an extraordinary rate — roughly 700 to 1,000 new synapses per second during the first few years of life. This massive construction project requires enormous amounts of sleep, particularly REM sleep, which is when the brain consolidates new learning and prunes unnecessary connections.

As the brain matures through adolescence, the need for total sleep hours gradually decreases, but the need for specific types of sleep shifts. Teenagers require extended REM periods for emotional development and memory consolidation during a time of intense cognitive growth. Their circadian clocks also shift later due to hormonal changes during puberty, a phenomenon called delayed sleep phase.

In adulthood, sleep stabilizes around 7 to 9 hours. The primary functions shift toward physical restoration, immune maintenance, and clearing metabolic waste from the brain through the glymphatic system. Deep sleep (slow-wave sleep) is critical during these years for tissue repair, hormone regulation, and cardiovascular health.

As adults age past 60, the architecture of sleep changes again. The suprachiasmatic nucleus — the brain's master clock — weakens with age, leading to earlier wake times, lighter sleep, and more frequent nighttime awakenings. This is not because older adults need less sleep; rather, their ability to generate consolidated sleep declines. The need for restorative sleep remains, even as the body becomes less efficient at producing it. Research from the National Institutes of Health confirms that age-related sleep changes are universal across populations, though their severity varies with lifestyle and health factors.

Complete Sleep Recommendations by Age

The National Sleep Foundation (NSF) convened a panel of 18 scientists and researchers in 2015 to produce the most comprehensive age-based sleep recommendations to date. Their findings, published in the journal Sleep Health, remain the gold standard referenced by pediatricians, sleep specialists, and public health organizations worldwide. The American Academy of Sleep Medicine (AASM) published similar consensus guidelines in 2016, largely aligning with the NSF ranges.

The "May Be Appropriate" column acknowledges individual variation. Some people genuinely function well outside the standard range due to genetic factors, activity level, or health conditions. However, the recommended range applies to the vast majority of people in each age group. You can enter your exact age into our sleep by age calculator to see where you fall.

Newborns (0–3 Months)

Newborns spend most of their existence asleep — between 14 and 17 hours per day. But this sleep looks nothing like adult sleep. It arrives in short bursts of 1 to 3 hours, scattered across day and night with no regard for the clock. This is because the circadian rhythm has not yet developed. The suprachiasmatic nucleus, the brain region responsible for syncing sleep to the light-dark cycle, does not mature until around 3 to 4 months of age.

What makes newborn sleep especially unique is its composition. Approximately 50% of a newborn's sleep is active sleep (the precursor to REM), compared to about 20 to 25% in adults. This outsized proportion of REM-like sleep is believed to serve as internal stimulation for the rapidly developing brain, compensating for the limited sensory input during waking hours.

Parents should avoid trying to impose a schedule on newborns. At this age, sleep is demand-driven. Feeding, diaper changes, and brief periods of wakefulness punctuate sleep sessions. The best approach is to follow the baby's cues, ensure a safe sleep environment (firm mattress, no loose bedding), and prioritize back sleeping to reduce SIDS risk. The Centers for Disease Control and Prevention recommends a bare crib with a firm, flat mattress as the safest sleep surface for newborns.

Newborns also lack sleep cycles as adults know them. Instead of the typical 90-minute adult cycle, newborn sleep cycles last roughly 50 to 60 minutes and alternate between active sleep and quiet sleep. These shorter cycles mean newborns wake more frequently, which is both normal and necessary for feeding.

Infants (4–11 Months)

Between 4 and 11 months, sleep begins to consolidate. Infants need 12 to 15 hours of total sleep, and an important milestone occurs during this period: most infants develop the ability to sleep for longer continuous stretches at night, sometimes 6 to 8 hours by 6 months of age.

The circadian rhythm becomes functional around 3 to 4 months, meaning infants start distinguishing day from night. Melatonin production kicks in, and cortisol patterns begin to follow a daily cycle. This is when establishing consistent sleep routines becomes both possible and beneficial. A regular bedtime ritual — dimming lights, a warm bath, a quiet feeding — helps signal to the developing brain that nighttime sleep is approaching.

Sleep architecture shifts as well. Active sleep begins transitioning into true REM sleep, and sleep stages become more differentiated. Sleep cycles lengthen to approximately 60 to 70 minutes. Naps typically settle into a pattern of two to three per day, totaling 3 to 4 hours of daytime sleep.

A significant concern during this stage is the "4-month sleep regression," when many infants who were sleeping well suddenly begin waking frequently. This is actually a developmental progression: the infant's sleep architecture is reorganizing to include more adult-like stages, including lighter Stage 1 and Stage 2 sleep. During these lighter phases, babies are more easily aroused and may need to learn to self-soothe back to sleep.

Toddlers (1–2 Years)

Toddlers need 11 to 14 hours of total sleep per day, typically split between nighttime sleep (10 to 12 hours) and one or two daytime naps. By 18 months, most toddlers transition from two naps to one, consolidating their daytime sleep into a single afternoon nap of 1 to 3 hours.

This is a critical period for sleep habit formation. Toddlers are developing autonomy and will often resist bedtime as they discover they can say "no." Sleep onset associations — the conditions a child learns to connect with falling asleep — become especially important. If a toddler always falls asleep being rocked, they may need rocking to return to sleep after normal nighttime awakenings.

Deep sleep remains abundant during the toddler years, supporting the physical growth that occurs during this period. Growth hormone is released primarily during deep sleep (Stage N3), and toddlers who are chronically sleep-deprived may show slower physical growth and reduced immune function.

Behaviorally, inadequate sleep in toddlers manifests as hyperactivity rather than the sluggishness adults experience. A toddler who seems "wired" at bedtime may actually be overtired, having missed the window when their sleep drive was strong enough to facilitate easy sleep onset. Watching for early drowsiness cues — rubbing eyes, yawning, becoming clingy — and starting the bedtime routine promptly can prevent this cycle.

Preschoolers (3–5 Years)

Preschoolers need 10 to 13 hours of total sleep. Many children in this age range still nap, though the need for daytime sleep decreases. By age 5, most children have dropped their nap entirely, consolidating all sleep into the nighttime period.

Sleep plays a particularly important role in preschool learning. Research from the University of Massachusetts Amherst found that naps significantly improved memory recall in preschoolers who were taught new information. Children who napped after a learning session retained 10% more material compared to those who stayed awake. The study suggests that for children who still nap naturally, the nap serves an active role in memory consolidation that nighttime sleep alone cannot replace.

Nightmares and night terrors peak during the preschool years. Nightmares occur during REM sleep and are remembered upon waking. Night terrors occur during deep sleep transitions, involve screaming or thrashing, and are typically not remembered. While frightening for parents, both are normal developmental occurrences that generally resolve without intervention. The Mayo Clinic notes that night terrors affect approximately 40% of children and most outgrow them by adolescence.

Parasomnias like sleepwalking and sleep talking also emerge during this period, often triggered by sleep deprivation, irregular schedules, or fever. Ensuring adequate total sleep and consistent bedtimes reduces the frequency of these events significantly. If a preschooler's bedtime consistently results in resistance lasting more than 30 minutes, the bedtime may be set too early for their individual sleep drive.

School-Age Children (6–13 Years)

School-age children need 9 to 11 hours of sleep. This is the age group where the gap between sleep need and actual sleep begins to widen. Homework, extracurricular activities, screen time, and social pressures all compete for the hours that should be devoted to rest.

A 2024 study published in JAMA Pediatrics found that only 58% of children aged 6 to 12 consistently met sleep recommendations, with screen use being the strongest predictor of insufficient sleep. Each additional hour of screen time before bed was associated with 15 fewer minutes of sleep and delayed sleep onset by approximately 20 minutes. The CDC has identified children's sleep insufficiency as a growing public health concern.

Cognitively, this age group is in a critical period for academic learning, and the relationship between sleep and school performance is well-documented. Children who sleep less than 9 hours show measurable deficits in attention, working memory, and processing speed. These effects are cumulative — chronic mild sleep restriction over a school year produces greater cognitive impairment than a single night of total sleep deprivation.

Sleep architecture during these years is characterized by abundant deep sleep, particularly in the first half of the night. This deep sleep supports physical growth and immune system development. Growth hormone secretion peaks during N3 sleep, and children who are growing rapidly (such as during pre-pubertal growth spurts) may temporarily need more sleep than their peers.

Parents should aim for a consistent bedtime between 7:30 and 9:00 PM for this age group, depending on wake time requirements. Electronics should be removed from the bedroom entirely, and the hour before bed should be spent on calming activities like reading or quiet conversation. Our bedtime calculator can help determine the ideal lights-out time based on your child's morning alarm.

Teenagers (14–17 Years)

Teenagers need 8 to 10 hours of sleep, but few get it. The average American teenager sleeps just 7 hours on school nights — a full hour below the minimum recommendation. This shortfall is not primarily caused by poor discipline or excessive screen use (though both contribute). It is driven by a fundamental biological shift in the circadian clock.

During puberty, the timing of melatonin secretion shifts approximately 2 hours later. A teenager's brain does not begin releasing melatonin until around 10:30 to 11:00 PM, compared to 8:00 to 9:00 PM in younger children. This means that asking a 15-year-old to fall asleep at 9:00 PM is biologically equivalent to asking an adult to fall asleep at 7:00 PM — the sleep drive simply is not there yet.

Combined with school start times that often require waking at 6:00 AM or earlier, this creates chronic sleep restriction. The consequences are serious: increased risk of depression, anxiety, obesity, impaired academic performance, and higher rates of drowsy driving accidents. Motor vehicle crashes are the leading cause of death for teenagers, and fatigue is a contributing factor in an estimated 100,000 police-reported crashes annually in the United States.

The American Academy of Pediatrics has recommended that middle and high schools start no earlier than 8:30 AM, but as of 2026, most American school districts have not implemented this change. In districts that have, the results have been striking: later start times are associated with improved attendance, higher test scores, reduced depression rates, and fewer car accidents among teen drivers. You can learn more about managing accumulated sleep debt from chronic restriction.

Young Adults (18–25 Years)

Young adults need 7 to 9 hours of sleep. This age group faces unique sleep challenges driven by major life transitions: college, first jobs, irregular social schedules, and often the first experience of complete autonomy over sleep timing.

College students are among the most sleep-deprived demographics. A 2023 study from the American College Health Association found that 60% of college students reported "poor" sleep quality, and only 11% reported sleeping well consistently. Academic demands, social activities, part-time work, and screen habits combine to push sleep into the margins of daily life.

The biological clock in young adults remains slightly later than in older adults, though it has begun to advance from its teenage peak delay. Most young adults have a natural sleep window of roughly 11:00 PM to 7:00 AM, though individual chronotype (whether you are a natural early bird or night owl) introduces significant variation. Use our wake-up calculator to find optimal rising times based on your personal schedule.

Sleep quality during these years is generally excellent — when young adults actually sleep. Deep sleep remains abundant, REM periods are well-structured, and the ability to recover from acute sleep loss is strong. However, the habits formed during this period tend to persist. Young adults who establish consistent sleep schedules in their early twenties are more likely to maintain good sleep health through middle age.

Alcohol deserves special mention for this age group. While alcohol is a sedative and helps people fall asleep faster, it dramatically disrupts sleep architecture. It suppresses REM sleep during the first half of the night, then causes a rebound effect in the second half that leads to fragmented, non-restorative sleep. A night of drinking followed by 8 hours in bed may yield only 5 to 6 hours of effective sleep. Caffeine is another common disruptor in this demographic, with many young adults relying on it to compensate for insufficient sleep.

Adults (26–64 Years)

Adults need 7 to 9 hours of sleep per night. This broad age range encompasses several decades of gradual change, so it is worth breaking it down further. In your thirties, sleep architecture remains similar to your twenties, though deep sleep begins a slow decline that will continue for the rest of your life. By your mid-forties, you may notice that you sleep less deeply and wake more easily to noise or temperature changes.

The most significant challenge for adults in this age range is not biological — it is lifestyle. Work demands, parenting responsibilities, financial stress, and the temptation to sacrifice sleep for productivity create a culture of chronic sleep restriction. The Centers for Disease Control and Prevention reports that approximately 35% of American adults regularly sleep less than 7 hours per night.

The health consequences of long-term sleep deprivation in adults are extensive and well-documented. Sleeping fewer than 6 hours per night on a regular basis is associated with a 48% higher risk of developing or dying from heart disease, a 15% greater risk of stroke, and significantly elevated rates of type 2 diabetes, obesity, and depression. The relationship between sleep and all-cause mortality follows a U-shaped curve: both too little (under 6 hours) and too much (over 9 hours) sleep correlate with increased mortality risk, though the mechanisms differ.

For adults in this range, consistency matters more than raw duration. Going to bed and waking at the same time every day — including weekends — strengthens the circadian rhythm and improves sleep efficiency. A person who sleeps 7 consistent hours is generally better off than one who sleeps 5 hours on weeknights and 10 on weekends, because the irregular pattern disrupts circadian timing in much the same way as jet lag. Track your patterns with our sleep debt calculator to quantify your accumulated deficit.

Seniors (65+ Years)

Older adults need 7 to 8 hours of sleep, but this number is deceptive because the nature of sleep changes substantially after 65. The suprachiasmatic nucleus — the brain's circadian pacemaker — deteriorates with age, leading to advanced sleep phase (wanting to sleep and wake earlier), reduced melatonin production, and less distinct circadian signaling.

Deep sleep declines most dramatically with age. A 25-year-old might spend 20% of the night in N3 deep sleep, while a 70-year-old may spend less than 5%. This reduction means that sleep is lighter overall, and nighttime awakenings become far more common. Older adults may wake 3 to 5 times per night, compared to once or twice for younger adults. These awakenings are often brief, but they fragment sleep and reduce its restorative quality.

The perception that older people "need less sleep" is largely a myth. What changes is the ability to obtain consolidated, uninterrupted sleep — not the underlying need for it. Studies that measure both sleep opportunity and daytime alertness in older adults consistently find that those who achieve 7 to 8 total hours (even if partially through naps) perform better cognitively than those who sleep less.

Sleep disorders also increase sharply with age. Sleep apnea affects an estimated 56% of adults over 65. Restless legs syndrome, periodic limb movements, and insomnia all become more prevalent. These conditions reduce effective sleep time even when time in bed appears adequate. Any senior experiencing persistent daytime sleepiness, loud snoring, or gasping during sleep should seek evaluation from a sleep medicine specialist.

Medications commonly prescribed to older adults, including beta-blockers, diuretics, corticosteroids, and certain antidepressants, can also disrupt sleep. If sleep quality changes after starting a new medication, discussing timing or alternatives with a physician is worthwhile. Harvard Health maintains an updated resource on medications that affect sleep.

Sleep Architecture Changes Across the Lifespan

One of the most profound ways age affects sleep is through changes in sleep architecture — the proportion of time spent in each sleep stage. Understanding these shifts helps explain why sleep feels different at 60 than it did at 20, even if total duration is similar. The following visualization shows how the composition of a typical night's sleep changes from birth through old age.

Several patterns emerge from this visualization. First, REM sleep declines from roughly half of all sleep in newborns to about 17% in seniors. Second, deep sleep (N3) peaks during childhood at approximately 25% and drops to as little as 5% in older adults — a reduction that is strongly linked to age-related memory decline. Third, time spent awake during the night increases dramatically with age, from virtually zero in children to 20% or more in seniors. This last point explains why an older adult who spends 8 hours in bed may only achieve 6 to 6.5 hours of actual sleep.

For a deeper understanding of how these stages function, visit our complete guide to sleep cycles or use the sleep cycle calculator to plan your night around optimal cycle completion.

Growth Hormone, Sleep, and Age

Human growth hormone (HGH) is one of the most important hormones regulated by sleep, and its relationship with sleep changes markedly across the lifespan. Understanding this relationship explains why sleep is so critical for physical development in children and why deep sleep decline in older adults has wide-ranging health consequences.

In children and adolescents, approximately 75% of total daily growth hormone is secreted during deep sleep (Stage N3), with the largest pulse occurring within the first 1 to 2 hours after sleep onset. This is the primary reason why sleep deprivation in children can directly impair physical growth. Studies published in the Journal of Clinical Endocrinology & Metabolism have documented cases of growth failure in children with chronic sleep disorders that reversed once the sleep disorder was treated.

In young adults (18–30), growth hormone continues to play an important role, shifting from promoting height growth to supporting muscle repair, tissue recovery, bone density maintenance, and fat metabolism. Athletes in this age group who sleep fewer than 7 hours show measurably reduced muscle protein synthesis and longer recovery times from training. This is why sleep is considered a performance-enhancing strategy in sports science.

In middle-aged adults (30–60), growth hormone secretion declines by approximately 14% per decade. This decline parallels the reduction in deep sleep, creating a feedback loop: less deep sleep means less HGH, which contributes to increased body fat, reduced muscle mass, decreased bone density, and slower wound healing. While growth hormone replacement therapy exists, optimizing deep sleep through good sleep hygiene is the first and safest intervention.

In older adults (60+), growth hormone levels may be 80% lower than at age 20. The near-absence of deep sleep in many seniors means the primary window for HGH secretion is severely curtailed. This contributes to sarcopenia (age-related muscle loss), osteoporosis, and the slower healing that characterizes aging. Exercise — particularly resistance training — is one of the few interventions that can partially restore both deep sleep and HGH secretion in older adults.

Pregnancy Sleep Needs by Trimester

Pregnancy represents a unique period in which sleep needs increase significantly, yet the ability to sleep well is often compromised by physical and hormonal changes. The National Sleep Foundation recommends that pregnant women aim for 8 to 10 hours of total sleep per day, but the specific challenges and strategies differ by trimester.

Sleep disturbance during pregnancy is extremely common — studies cited by the National Institutes of Health indicate that up to 78% of pregnant women report sleep problems, with prevalence highest in the third trimester. Importantly, poor sleep during pregnancy is not merely an inconvenience. Research links chronic sleep deprivation during pregnancy to increased risk of gestational diabetes, preeclampsia, longer labor durations, and higher rates of cesarean delivery.

Restless legs syndrome (RLS) deserves special mention, as pregnancy-related RLS affects an estimated 26% of women in the third trimester — roughly four times the rate in the general adult population. RLS during pregnancy is often linked to iron deficiency and typically resolves within weeks of delivery. Iron supplementation under medical supervision may provide relief.

Sleep position becomes medically relevant from the second trimester onward. Left-side sleeping is recommended after 20 weeks because it optimizes blood flow through the inferior vena cava to the placenta. Back sleeping in late pregnancy has been associated with a modestly increased risk of stillbirth in some studies, though the absolute risk remains very low. Use our sleep calculator to ensure you are allowing enough time for sleep given the increased need and fragmentation of pregnancy.

The Teen Sleep Crisis and School Start Times

The mismatch between teenage biology and school schedules has created what researchers call a public health epidemic. Understanding the scope of this problem is important for parents, educators, and teens themselves.

The biological facts are not in dispute. Puberty triggers a delay in the circadian clock of 1 to 3 hours, depending on the individual. Melatonin onset shifts later, cortisol rhythms adjust, and the sleep pressure system (homeostatic sleep drive) changes so that teens can stay awake longer without feeling drowsy. These changes are not under conscious control. Telling a teenager to "just go to bed earlier" is like telling an adult to fall asleep at 5 PM — the brain is not ready.

Meanwhile, many high schools begin at 7:00 or 7:30 AM, requiring wake times of 5:30 or 6:00 AM. If a teenager's brain does not release melatonin until 11:00 PM and they cannot realistically fall asleep before 11:30 PM, a 6:00 AM alarm gives them 6.5 hours of sleep. This falls below the minimum recommended 8 hours by a significant margin, and it happens five days per week for the entire school year.

The consequences accumulate throughout adolescence. Chronic sleep restriction in teenagers is associated with a 25% increase in symptoms of depression, a threefold increase in the risk of obesity, impaired immune function, reduced athletic performance, and measurably lower academic achievement. Sleep-deprived teens are also more likely to engage in risk-taking behavior, including substance use and reckless driving.

Evidence for Later School Start Times

The data supporting later start times is now substantial. A landmark study by the American Academy of Sleep Medicine followed school districts that shifted start times to 8:30 AM or later and documented the following outcomes:

What can be done if school start times cannot be changed? Families can focus on optimizing the sleep that is available: eliminating screens for at least one hour before bed (blue light further delays melatonin onset), maintaining consistent weekend wake times within 1 hour of weekday times, keeping bedrooms cool and dark, and avoiding caffeine after noon. Strategic weekend catch-up sleep — sleeping 1 to 2 hours longer, but not more — can partially mitigate the debt without severely disrupting the circadian rhythm. Track the deficit with our sleep debt calculator.

Senior Sleep Challenges and Solutions

Sleep in the later decades of life is characterized by several predictable changes that, while normal, can significantly impact quality of life if not managed properly. According to Harvard Health Publishing, nearly half of adults over 60 report some degree of insomnia, making sleep one of the most common complaints in geriatric medicine.

For seniors who cannot achieve 7 hours of consolidated nighttime sleep, our power nap guide offers evidence-based strategies for supplementing with a short daytime nap without disrupting the following night.

Cultural Differences in Children's Bedtimes

While biology determines how much sleep children need, culture heavily influences when they get it. Bedtime practices vary dramatically across countries, and these differences have implications for total sleep duration, family routines, and even children's health outcomes. Understanding these patterns can help parents evaluate their own practices in a broader context.

Data compiled from the Journal of Sleep Research multi-country survey (Mindell et al., 2010) and subsequent cross-cultural studies. The pattern is clear: countries with earlier bedtimes tend to produce children who meet or exceed the NSF sleep recommendations, while countries with later bedtimes consistently fall short.

How to Use the Sleep-by-Age Calculator

Our sleep by age calculator includes a dedicated age-based mode that adjusts its recommendations based on your specific age group. Here is how to get the most from it:

1. Select the "Sleep by Age" tab on the calculator interface. This mode automatically pulls NSF-recommended ranges for the age you enter.
2. Enter the sleeper's age — this can be for yourself, your child, or anyone else. The calculator recognizes all age brackets from newborn through 65+.
3. Enter the desired wake time or bedtime depending on which direction you want to calculate. If you know your child needs to wake at 6:30 AM for school, enter that time to see recommended bedtimes.
4. Review the recommended sleep window, which adjusts the number of sleep cycles based on age-appropriate duration and cycle length.
5. Note the highlighted recommendations — the calculator marks the bedtimes that fall within the NSF-recommended range for the entered age, making it easy to identify the best options.

For children under 3, the calculator accounts for the fact that total sleep includes both nighttime sleep and naps. It will indicate total daily sleep needs and suggest nighttime durations that leave room for age-appropriate napping.

For teenagers, the calculator factors in the delayed circadian phase by noting that the recommended bedtime may feel "too early." It encourages working backward from the latest feasible wake time rather than trying to impose an artificially early bedtime.

For seniors, the calculator acknowledges that achieving 7 to 8 hours of consolidated nighttime sleep may not be realistic and suggests supplementing with a short afternoon nap if nighttime sleep falls below 6 hours.

You can also use our wake-up calculator to find the best alarm time given a specific bedtime, or the sleep cycle calculator for a cycle-based approach that works regardless of age.

Signs You Are Not Getting Enough Sleep

Sleep deprivation does not always feel like exhaustion. Many people have been underslept for so long that they have normalized the symptoms. The following signs indicate insufficient sleep, regardless of how many hours you think you are getting:

• Needing an alarm to wake up: A well-rested person wakes naturally within a few minutes of their habitual alarm time. If you cannot wake without one, you are likely not sleeping enough or your timing is misaligned. Try our best time to wake up guide to realign your schedule.
• Falling asleep within 5 minutes: Contrary to popular belief, falling asleep instantly is a sign of sleep deprivation, not good sleep ability. Healthy sleep onset takes 10 to 20 minutes.
• Microsleeps during the day: Brief involuntary episodes of sleep lasting 1 to 30 seconds, often disguised as "zoning out," are a hallmark of significant sleep debt.
• Increased irritability and emotional reactivity: The prefrontal cortex, which regulates emotional responses, is especially sensitive to sleep loss. Overreacting to minor frustrations is a reliable indicator. Learn more about the connection in our sleep and mental health guide.
• Difficulty concentrating or remembering: Sleep is essential for memory consolidation. Chronic undersleeeping produces progressive difficulty with focus, recall, and learning new information.
• Frequent illness: Sleep deprivation suppresses immune function. People sleeping less than 7 hours are three times more likely to develop a cold when exposed to the rhinovirus compared to those sleeping 8 or more hours, according to research published by the National Institutes of Health.
• Craving sugar and carbohydrates: Sleep loss disrupts hunger hormones (ghrelin and leptin), increasing appetite for calorie-dense foods as the body attempts to compensate for low energy. Our sleep and weight loss guide explores this relationship in detail.
• Increased clumsiness and slowed reactions: Motor coordination degrades with sleep loss. After 17 hours of continuous wakefulness, reaction time impairment is comparable to a blood alcohol level of 0.05%, according to research from the CDC.

In children, the signs are different. Sleep-deprived children often become hyperactive and oppositional rather than sluggish. Teachers may mistake sleep deprivation for ADHD because the behavioral presentations overlap significantly. If a child is struggling with attention and behavior, evaluating their sleep should be the first step before any other assessment.

Sleep Cycles Across Age Groups

The structure of a single sleep cycle varies considerably by age, which is why a sleep calculator must account for more than just total hours.

The progression is clear: cycles lengthen from about 50 minutes in newborns to 90 minutes by school age and remain around 90 minutes into old age. REM sleep decreases proportionally from half of all sleep in newborns to roughly a fifth in adults. Deep sleep peaks in childhood and declines steadily from young adulthood onward.

This is why simply counting "90-minute cycles" does not work for young children. A toddler's sleep cycles are shorter, so the same number of hours contains more cycles and more transitions between sleep stages. A sleep calculator designed for children must use age-appropriate cycle durations to generate accurate recommendations. Our sleep cycle calculator accounts for these differences.

Nap Needs by Age

Daytime napping is a normal and necessary part of sleep for young children, serves a transitional role in adolescence, and can be either helpful or harmful in adulthood depending on timing and duration.

For adults, the key distinction is between intentional short naps and unintentional long ones. A planned 20-minute power nap before 3 PM can improve alertness, mood, and performance without affecting nighttime sleep. However, napping for 60 minutes or more, or napping after 4 PM, tends to reduce sleep pressure and make falling asleep at bedtime more difficult.

For older adults, a single short afternoon nap (sometimes called a "siesta") is generally beneficial and may compensate for the fragmented nighttime sleep common in this age group. However, excessive daytime sleeping (more than an hour total) in seniors has been associated with increased risk of cognitive decline and may indicate an underlying sleep disorder that should be evaluated. For more on alternative sleep schedules, including biphasic and polyphasic approaches, see our dedicated guide.

Frequently Asked Questions

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Research References

The recommendations and data in this guide are drawn from peer-reviewed research and official guidelines from major health organizations. Below are key references for further reading.

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