Most babies start sleeping longer stretches of 6 to 8 hours between 4 and 6 months old, but the timeline varies widely. At 6 months, more than half of babies still aren’t sleeping 8 consecutive hours. By 12 months, about 43% still aren’t hitting that mark. If your baby isn’t sleeping “all night” yet, that’s not a problem to solve. It’s well within the range of normal.
What “Sleeping Through the Night” Actually Means
Here’s something most parents don’t realize: even babies who “sleep through the night” still wake up multiple times. Every human cycles through lighter and deeper phases of sleep, and brief wakings between cycles are normal at any age. The real milestone isn’t sleeping without waking. It’s waking briefly and falling back asleep without needing you to intervene.
The American Academy of Pediatrics makes the point clearly: a good sleeper at this age is a baby who wakes frequently but can get back to sleep on their own. Prolonged, undisturbed sleep in very young infants isn’t actually healthy, because those brief wakings serve a protective function, allowing the baby to rouse if breathing becomes compromised.
So when other parents tell you their baby sleeps through the night, what they usually mean is their baby wakes, resettles quietly, and nobody has to get out of bed. That’s a very different thing from 10 uninterrupted hours of unconsciousness.
The Biological Pieces That Need to Fall Into Place
Three things have to develop before a baby can sleep long stretches: an internal body clock, a stomach big enough to go hours without food, and the ability to self-soothe.
Newborns have no circadian rhythm. Their bodies don’t yet follow a day-night cycle. Around 8 to 9 weeks, the hormones that regulate sleep and wakefulness (melatonin, which promotes drowsiness, and cortisol, which promotes alertness) begin following a predictable pattern tied to light and dark. This is why many parents notice the first hints of a schedule emerging around 2 months.
Stomach size is the other bottleneck. A newborn’s stomach holds roughly a tablespoon. By 1 to 3 months, it’s grown to 4 to 6 ounces. Between 3 and 6 months, it reaches 6 to 7 ounces, which is finally enough to sustain a baby through a longer stretch without hunger waking them up. This is why night feedings are genuinely necessary in the early months, not a habit to break.
The third piece, self-soothing, develops gradually. Newborns simply can’t regulate their own emotions or calm themselves down. Over the first several months, babies begin developing the ability to fall asleep independently and resettle when they wake between sleep cycles. Some babies figure this out earlier, some later.
What the Numbers Look Like Month by Month
Research tracking large groups of infants found that at 6 months old, about 38% of babies were not yet sleeping even 6 consecutive hours at night. Roughly 57% were not sleeping 8 hours straight. By 12 months, those numbers improve but don’t disappear: 28% still weren’t managing 6 consecutive hours, and 43% weren’t reaching 8.
These numbers are worth sitting with, because the cultural expectation that babies “should” sleep through the night by 6 months doesn’t match what most babies actually do. If your 9-month-old is still waking once or twice, you’re in the company of a very large percentage of parents.
Why Breastfed Babies Often Take Longer
Breastfed babies tend to sleep in shorter stretches than formula-fed babies, and this is a consistent finding across studies. The reason is straightforward: breast milk digests faster than formula, and breastfed infants typically take smaller volumes at each feeding. That means they get hungry again sooner.
Formula-fed babies often consolidate their sleep earlier because the slower digestion keeps them full longer. This doesn’t make formula better for sleep or breastfeeding a problem. It’s just a physiological difference worth knowing about so you’re not comparing your breastfed baby’s sleep to a formula-fed baby’s and worrying unnecessarily.
Sleep Regressions and Why Progress Isn’t Linear
Even after your baby starts sleeping longer stretches, expect setbacks. Sleep regressions are periods of worse sleep lasting roughly two to four weeks, and they’re common throughout the first year and beyond. They’re not tied to specific ages as neatly as many sleep charts suggest. Instead, they’re tied to what your baby is going through at any given time.
Common triggers include growth spurts (which create genuine hunger), reaching new physical milestones like rolling over or pulling up (babies often want to stay awake and practice), teething pain, illness, and changes in routine like travel or starting daycare. Separation anxiety becomes a particularly strong disruptor around 9 months, when babies develop a sharper awareness that you exist even when you’re not visible.
A baby who slept 7 hours straight at 5 months may start waking three times a night at 6 months when they learn to sit up. This isn’t a sign that something went wrong. It’s a temporary disruption caused by a brain that’s busy rewiring itself.
What Helps Babies Sleep Longer
You can’t force the biological timeline, but you can support it. The most effective thing you can do is give your baby opportunities to practice falling asleep on their own. This means putting them down drowsy but still awake when possible, so they begin associating their sleep space with the process of falling asleep rather than associating your arms or a feeding with it.
Consistent bedtime routines matter more than most parents expect. A predictable sequence of events (bath, feeding, dimmed lights, a short book or song) signals to the developing circadian system that sleep is coming. Keeping the room dark and boring during nighttime wakings, and bright and social during the day, reinforces the day-night distinction that young brains are still learning.
For safe sleep, the guidelines are firm: babies should sleep on their backs, on a flat and firm surface, with no loose blankets, pillows, stuffed animals, or bumpers. Avoiding soft sleep surfaces like couches and recliners is especially important, because these carry a high suffocation risk even when a parent is present.
The Wide Range of Normal
Some babies sleep 8-hour stretches by 3 months. Others are still waking at 14 months. Both can be perfectly healthy. Temperament plays a role, as does feeding method, how easily a baby is stimulated, and whether they’re in the middle of a developmental leap. Premature babies often reach sleep milestones later when you adjust for their corrected age.
The 6-month mark gets repeated so often that it starts to feel like a deadline, but nearly six out of ten babies haven’t hit the 8-hour milestone at that age. If your baby is gaining weight normally, developing on track, and getting enough total sleep across 24 hours (typically 12 to 16 hours for infants under a year), the pattern of that sleep matters less than you might think. Longer stretches will come as the brain, body, and digestive system mature on their own schedule.