Somewhere on your phone there is a chart that says a six-month-old needs about thirteen hours of sleep a day. The chart is not wrong. It is just describing the middle of a very wide range, and almost nobody sits exactly in the middle.
The actual range
The largest pooled review of normal infant sleep, drawing on studies of thousands of healthy babies, gives the following at around six months. The average total sleep in twenty-four hours is a little under thirteen hours. The normal range — the band that captures ninety-five percent of healthy babies — runs from 8.8 hours to 17 hours. That is an eight-hour spread, and every baby inside it is normal.
Daytime sleep is even wider. In one long-running reference study, daytime sleep at six months ranged from about twenty-five minutes to over six hours across healthy babies. Night wakings at three to six months average under one a night in the pooled data, with a normal range from none up to about three. The longest stretch of sleep in the second half of the first year averages around eight hours, with a normal range from three hours to nearly fourteen.
Two more things worth knowing about those numbers. First, two well-respected reference sources disagree with each other by roughly an hour at the same ages, because they measured different populations with different tools — neither is “right”. Second, nearly all of this data comes from asking parents, and parents systematically over-report sleep by fifteen to fifty minutes, because they cannot see a waking they slept through.
“Sleeping through” at six months
At six months, fewer than half of babies manage eight consecutive hours on a given night. In one large cohort, fifty-seven percent of six-month-olds did not sleep eight hours straight — and the same study checked whether that mattered, comparing developmental testing and mothers’ mood between the babies who did and didn’t. It found no difference.
“Sleeping through” is also not a switch that flips. Across thirteen consecutive nights in a group of six-month-olds, only one baby managed eight hours every single night, and half never did. A good week followed by a bad week is the expected shape.
What is typical, loosely
By around five to seven months, sleep tends to organise into roughly two naps of about an hour and a half each, plus a night of around ten and a half hours — with all the variation above wrapped around that. Morning wake time becomes surprisingly fixed from about five months, which has a practical consequence: a later bedtime usually subtracts sleep rather than shifting it.
Nap transitions are where popular advice gets most confident and the research gets quietest. No peer-reviewed study identifies an age at which babies drop from three naps to two. The only nap transition with a published anchor is the move from two naps to one, which the evidence puts at fifteen to twenty-four months — wider and later than the “thirteen to fifteen months” that circulates.
What to look at instead of the chart
The question that matters is not whether your baby matches a number. It is whether your baby seems well and is growing, whether they are broadly content when awake, and whether this is sustainable for you. If the answer to those is yes, a baby who sleeps ten and a half hours a day and a baby who sleeps fifteen are both fine.
If you want something to track, track what you can actually change and feel: how long settling takes at bedtime, how much of the night you are up, and how you are functioning. Those are the things a routine and a plan reliably improve. Total hours mostly aren’t.
When to ask a doctor
Growth is the anchor. If your pediatrician is happy with weight gain, most sleep variation is just variation. Snoring three or more nights a week, mouth breathing in sleep, pauses or gasping, unusual movements on waking, or a baby who is unwell rather than unsettled are for your pediatrician — not for a chart, and not for us.