How Long Are Sleep Cycles? Baby Sleep Cycle Guide by Age

What are infant sleep cycles and how do they work?

First things first: what is a sleep cycle? Well, a sleep cycle refers to the different stages of sleep we (or more specifically, our bodies and brains) go through during a single period of rest. Most people go through multiple sleep cycles across one “stretch” of sleep, without necessarily waking in between.

Each sleep cycle is made up of a combination of REM and non-REM (NREM) sleep, with the former being a lighter, often dream-filled sleep state where the brain is more active, and the latter made up of various stages more associated with deep sleep.

As you’ll know if you are (or have ever been) a parent, baby sleep cycles can be very different from adults’. For starters, they tend to be much shorter, particularly at the newborn stage, while the combination of REM vs NREM sleep for newborns is around 50/50 — in comparison, adult sleep is usually made up of 75-80% NREM sleep.

Infant sleep cycles evolve as they get older too, both in terms of length and makeup. For example, each sleep cycle will become longer, and the percentage of REM sleep (often called active sleep in babies) will decrease, meaning the older they are the more time they’ll spend in a deep, restful sleep state.

How long are sleep cycles in babies?

In newborns, sleep cycles usually last somewhere between 30 and 60 minutes — in contrast to a typical adult sleep cycle of around 90 to 110 minutes. These cycles are made up of around 50% active (or REM) sleep, where they tend to be more restless and prone to waking, and 50% quiet (or NREM) sleep, where they’ll be in a deeper, more restful sleep.

As babies get older, their sleep cycles gradually lengthen and their sleep patterns become a little more structured. From about 3 months onwards, babies start to adopt a more “adult” sleep cycle — each cycle may last closer to 60-90 minutes, while they also spend less time in REM sleep (around 30-40%) and more in deeper non-REM sleep.

When do babies start sleeping for longer periods?

By around 12 months, a baby’s sleep cycle will much more closely resemble that of an adult. Sleep cycles may last up to 90 minutes at a time, and the split between light REM and deep NREM sleep will skew even more towards the latter — as with most adults, each cycle will be made up of around 75-80% non-REM sleep.

Of course, this doesn’t mean your little one’s sleep schedule will become fully adult-like — they may still be sleeping up to 14 hours a day (double the recommended minimum of 7 hours for adults) and napping 1-2 times in the daytime — but how (and how long) they sleep during each cycle will be more in line with how grown-ups experience sleep.

Baby sleep cycles by age

In your baby’s first year, their sleep cycles will go through a series of evolutions, starting with shorter, more “active” sleep cycles and graduating to longer cycles made up of more deep, restorative sleep. Eventually, their sleep cycles will start to look a lot more “adult-like”.

While these timelines aren’t carved in stone (as with anything during early parenthood, few things are fixed or “normal”) and all babies move through sleep cycles slightly differently, you can usually see some patterns emerge as they age, with their sleep cycles beginning to crystallize from 3 months or so.

Not every baby will follow these patterns exactly, but the below is a good general guide:

Newborn (0-3 months) sleep cycle

A newborn may sleep for up to 18 hours a day, usually in short bursts with frequent waking. Their sleep cycles at this stage will be short — generally between 30 and 60 minutes — and they’ll typically spend the first 20-30 minutes of each cycle in active or REM sleep, which means they can appear restless and fidgety, before settling into a deeper “quiet” sleep.

At 0-3 months, your baby’s sleep patterns are usually characterized by:

• Short sleep cycles. Newborn sleep cycles tend to be no longer than 60 minutes at a time, sometimes lasting as little as 30 minutes.

• More time in “active” sleep. Typically, around 50% of a newborn’s sleep cycle will involve active or REM sleep, a lighter sleep state where restlessness is common.

• Many daytime naps. Newborn sleep occurs in short bursts, with frequent wake windows. Your baby may have 4-6 separate naps during the day, or even more.

• A lack of circadian rhythm. Newborns’ internal sleep-wake rhythms are not yet fully developed, so there’s no distinction between daytime and nighttime sleep. 

3-6 months sleep cycle

At this stage, your baby’s sleep cycles will start to increase in length, typically lasting between 60 and 90 minutes at a time. They may still sleep for up to 16 hours a day, but more of this will occur at night (though they’ll still be napping regularly during the day). The makeup of their sleep will start to change too, with around 60-70% of each cycle spent in deeper NREM sleep. 

At 3-6 months, your baby’s sleep habits may resemble something like this:

• Longer sleep cycles. Sleep cycles typically become longer from around 3 months onwards, with each cycle likely to last at least 60 minutes.

• Less time in “active” sleep. Your baby will start to spend more time in non-REM sleep (a deeper and more peaceful sleep state) and display less restlessness.

• More nighttime sleep. Around 3-4 months, melatonin production regulates (a hormone that supports the circadian rhythm), which means your baby will usually begin to sleep for longer during the night.

• Their circadian rhythms will begin to develop, which means they’ll usually spend longer sleeping during the night.

• More consistent nap patterns. Your little one should start to establish a more predictable nap routine, with 3-4 naps throughout the day.

6-12 months sleep cycle

From 6 months onwards, baby sleep cycles tend to become more “adult”. This doesn’t mean they’ll begin sleeping exclusively during the night, of course, but they may be down to just 2-3 daily naps. Each sleep cycle will last up to 90 minutes (which is about normal for an adult) and they’ll spend up to three-quarters of their snoozing time in a deeper, more restful sleep state.

At 6-12 months, babies’ sleep patterns have a few defining characteristics:

• Adult-like sleep cycles. From 6 months your baby’s sleep cycles are closer in length to an adult’s, with each cycle lasting around 70-90 minutes at a time.

• More time in deep sleep. Each sleep cycle will be split roughly 70/30 between deeper NREM sleep and lighter REM sleep.

• Fewer daytime naps. Your baby will typically sleep for longer at night, and they’ll normally be down to just two main naps in the daytime — some may be on a single nap from 10-12 months.

• Developmental disruptions. Development-related changes such as learning to sit up and crawl (along with factors like teething) can introduce temporary sleep disturbances.

12+ months sleep cycle

By the time your little one has reached toddlerdom (yes, it is a word), their sleep cycles will much more closely resemble those of an adult. Again, this doesn’t mean their sleep schedule will align with yours, but as with an adult each cycle will last roughly 90 minutes, and they’ll experience more NREM sleep too (around 75-80% per cycle). They’ll still likely be napping during the day, but you can usually transition them to a single daytime nap.

By 12 months and beyond, your baby’s sleep patterns will be more predictable:

• Solidified sleep cycles. Your baby’s sleep cycle will be roughly the same as an adult’s at this stage, with each cycle lasting around 90 minutes.

• Consistent REM / NREM pattern. Like adults, toddlers tend to experience around 75-80% deep (NREM) sleep, and 20-25% REM sleep.

• 1-2 daytime naps. Most toddlers will need just 1-2 naps a day, and will usually drop to a single nap between 10-18 months — though this can vary from child to child.

• Less frequent night waking. Most toddlers can sleep through the night and will wake less frequently.

Navigating your baby’s sleep patterns can sometimes feel like trying to solve a puzzle without all the pieces, but understanding the basics of their sleep cycles can provide much-needed clarity in the midst of sleepless nights.

While every baby is different, knowing what to expect as they grow will help you adjust to their changing sleep needs — whether that means embracing those early-day naps or celebrating the longer stretches of night sleep that eventually, mercifully arrive.

Remember, it’s all about patience, flexibility, and finding what works best for both you and your baby. By tuning into their unique sleep cues and rhythms, you’ll be better equipped to foster healthy sleep habits and, ultimately, even enjoy a little more rest yourself.

Reviewed by Sleep Consultant, Rosey Davidson in November 2024.