Most babies start sleeping through the night between 3 and 6 months of age, though “sleeping through the night” in infant sleep terms means a stretch of 6 to 8 hours, not the 10 or 12 hours adults often imagine. Some babies reach this milestone earlier, and a significant number don’t get there until closer to their first birthday. The variation is wide and normal.
What “Sleeping Through the Night” Actually Means
When pediatricians talk about an infant sleeping through the night, they’re not describing a child who sleeps 10 uninterrupted hours. They mean a stretch of roughly 6 to 8 consecutive hours. A baby who goes down at 10 p.m. and wakes at 4 a.m. has technically slept through the night, even though that feels like the middle of the night to you. Adjusting your expectations to this definition can make the milestone feel much closer than you think.
The Month-by-Month Timeline
Newborns sleep in short bursts of 1 to 3 hours around the clock. Their stomachs are tiny. A newborn’s stomach holds about 20 milliliters, roughly the size of a cherry, which means they need to eat approximately every hour to stay fueled. As the stomach grows over the first weeks, feeding intervals stretch, and so do sleep windows.
By about 8 to 9 weeks, a baby’s brain begins releasing the hormones that regulate sleep and wakefulness (melatonin and cortisol) on a more predictable schedule. This is the earliest point when you might notice a longer stretch forming at night, though it’s usually only 3 to 4 hours.
By 3 months, many babies are capable of a 6-hour stretch, particularly once they weigh 12 to 13 pounds. That weight threshold matters because a bigger body can store enough calories to go longer without a feeding. Between 3 and 6 months, most families see the longest sleep window gradually extend to 6 to 8 hours. But “most” is doing a lot of work in that sentence. Some babies don’t consolidate nighttime sleep until closer to 12 months, and that’s still within the normal range.
Why Feeding Method Matters
Breast milk digests faster than formula, so breastfed babies tend to wake more frequently for feedings in the early months. Formula-fed babies older than 6 months are unlikely to be waking from genuine hunger, since formula empties from the stomach more slowly. For breastfed babies, night feedings may remain nutritionally important up to 12 months.
That said, the relationship between feeding method and total sleep is more nuanced than the “formula helps babies sleep longer” advice you may have heard. A large study of over 4,500 infants found that babies who were exclusively breastfed for more than 3 months actually had better overall sleep patterns through their first two years. They logged more nighttime sleep at 3, 6, and 12 months compared to babies who were partially or fully formula-fed. Waking to eat and total sleep quality are two different things.
Sleep Regressions That Reset the Clock
Even babies who have been sleeping long stretches will hit periods where they suddenly start waking again. These regressions are predictable and temporary, but they can be exhausting.
The most common one hits around 4 months, when a baby’s sleep architecture matures and they start cycling through lighter and deeper stages of sleep the way adults do. They wake briefly between cycles and haven’t yet learned to fall back asleep on their own. This regression catches many parents off guard because it often arrives right when nighttime sleep was finally improving.
Around 9 months, separation anxiety becomes a factor. Babies at this age understand that you exist even when you leave the room, and they don’t love that realization at 2 a.m. Teething, growth spurts, learning to pull up or crawl, starting daycare, and illness can all trigger shorter regressions at any point. Most pass within a few days to two weeks.
When Sleep Training Can Help
If your baby is at least 4 months old and weighs around 14 pounds, sleep training is a reasonable option. Before that age, most babies aren’t developmentally ready to self-soothe, and they may still need nighttime calories.
The most studied approach is graduated extinction, sometimes called the Ferber method. You put the baby down awake and check on them at gradually increasing intervals, giving them space to learn to fall asleep independently. Most families see significant improvement within 7 to 10 days. Other methods exist on a spectrum from very hands-off to very gradual, and the best one is whichever approach you can follow consistently.
Sleep training teaches a baby to fall asleep on their own at bedtime, which also helps them resettle during normal nighttime awakenings. It doesn’t eliminate every waking, especially if the baby still needs a feeding, but it reduces the wakings that happen because the baby can’t get back to sleep without your help.
What You Can Do Right Now
Before your baby is ready for any formal sleep training, there are small things that help nudge nighttime sleep in the right direction. Expose your baby to natural daylight during the day and keep lights dim in the evening. This supports the circadian rhythm that’s developing around 8 to 9 weeks. Create a short, consistent bedtime routine so your baby begins to associate certain cues with sleep. Keep the sleep space simple: a firm, flat mattress with a fitted sheet, no loose blankets, pillows, or stuffed animals.
Pay attention to your baby’s individual pattern rather than comparing to milestone charts. A baby who is gaining weight well, eating enough during the day, and waking only once or twice at night at 5 months is doing exactly what a healthy baby does. The 3-to-6-month window is an average, not a deadline. Some perfectly healthy babies take longer, and that’s a reflection of their temperament and biology, not a problem to solve.