The one-nap transition: what the sources actually agree on
It is midday and the afternoon nap has turned into an hour of chatting, rolling and standing in the cot.
Ask six ranked pages when to drop to one nap and you get different answers, from 9–18 months at the widest to 12–15 months at the narrowest, none of them sourced beyond the author's own experience. What those same six pages agree on, in close detail, is what to actually watch for.
This article will not give you a corrected age of its own. It shows the published spread, where the sources actually agree, and how long the switch itself tends to take, so you can watch your baby rather than the calendar.
The age window nobody sources
Across the six UK-ranked pages read for this article, captured 16 September 2026, the stated windows span roughly 9 to 24 months. At the edges sit a 9–18 month window and a page that acknowledges 10–24 months in other books and websites before settling on around 14 to 15+ months from its own experience. Four of the six sit inside 12–18 months, the narrowest reading 12–15 months.
Not one of the six cites a study, dataset or clinical body for its own figure: each traces to "in our experience" or an individual consultant's practice. One US consultancy puts the disagreement more honestly than the rest:
"According to different baby sleep books and websites out there, babies drop to one nap anywhere from 10 months to 24 months old. These wide age ranges and contradictions make it hard for parents to figure out what to do." — Baby Sleep Site
That page then offers its own uncited figure, just like the rest. No page recommends judging readiness by age alone, not even the ones with the narrowest windows. That is worth holding on to.
What to watch for instead
This is the useful part. Where the numbers scatter, the day-to-day signs converge.
Fighting the second nap, consistently. Named by all six as the primary signal: not one tricky afternoon, but refusing, playing or crying through the nap over roughly one to three weeks. Two pages put a number on the pattern: a five-day streak repeated over two to three weeks on one, 10 to 14 consecutive days on another.
Naps changing length, or taking longer to settle. Named by four of six: 45 minutes or more to fall asleep, a shorter second nap, or a longer first nap trying to do the work of two.
Bedtime drifting later or getting harder. Named by three of six: wide awake until 8.30 or 9pm despite two good naps, or new split nights and broken stretches overnight.
Waking earlier in the morning. Named by four of six. One page calls it sleep maths: once daytime sleep no longer fits, the extra awake time often shows up first as an earlier start to the morning.
Coping happily with longer stretches awake. Named by three of six, in near-identical wording: comfortably awake four to five hours before and after the nap without becoming overtired. Alone it means little; alongside the other signs, it supports them.
If you try one nap and it falls apart, three pages say plainly: treat it as information, not failure. Go back to two naps for a week or two and try again. The move is rarely a straight line.
This is about daytime pattern only. If your baby is unwell, feeding poorly, or you are worried about growth, breathing in sleep or development, pause the nap question and speak to your GP or health visitor.
How long the wobble itself lasts
The second disagreement gets less attention, and it matters for tired evenings. Across the same six pages, the stated length for the transition runs from about two weeks to about six weeks, and again none of them sourced.
The shortest figure allows for the odd short afternoon nap along the way; the middle figures say two to three weeks on average, or up to a month. The longest, most detailed page gives a week-by-week shape: afternoons unsettled first, then the morning nap shifting later, then one nap stabilising. But it states two different totals on itself: four to six weeks in the body, three to six in its own FAQ. That inconsistency is worth noting for what it shows: even the most thorough source here is uncertain.
Expect a few unsettled weeks rather than a single switch-over night, with occasional two-nap days when nights have been short. What the pages share on making the shift: nudge the morning nap later in small steps until it sits around midday, bring bedtime a little earlier as wake stretches lengthen, and keep the plan loose enough to offer two naps if your baby is clearly flagging.
What the science actually says
None of the six ranked pages cites the one peer-reviewed paper on this transition. Spencer and Riggins, in the Proceedings of the National Academy of Sciences (2022), describe sleep turning from two daytime naps plus night sleep, by about nine months, to one nap as the morning nap fades, with timing varying from 6 to 18 months, wider and more cautious than most consultant pages. Their explanation, that a more efficient memory system reduces the pressure to sleep so naps drop away, is presented explicitly as a novel hypothesis with preliminary support from one very small study of eight children aged two to five, not settled fact.
Two of their points are worth keeping: "there are currently no formal recommendations regarding nap timing/length or nap transitions" from bodies like the American Academy of Pediatrics or the National Sleep Foundation, and sleep advice at this age increasingly comes from coaches who "lack evidence-based information and guidance on such issues." That is a ceiling on what anyone can claim with confidence, not a dismissal of the ranked pages.
The UK source we found is modest. NHS Healthier Together's Healthy Sleep page says toddlers' two naps usually become one of one to three hours, and that "by around 18 months old, most toddlers have one daytime nap." That is a soft ceiling, not a referee between any competing figure. The national NHS baby-sleep page we checked does not address nap counts at all.
Watch the cluster of signs above, not the calendar. A battle at the second nap and a later bedtime for a couple of weeks say more than any birthday. We have made this case before: behaviour beats birthdays. Our guide to sleep regression ages found the same pattern in regression timelines, and the one-nap evidence points the same way.
References
- Spencer, R.M.C. & Riggins, T. (2022). Contributions of memory and brain development to the bioregulation of naps and nap transitions in early childhood. Proceedings of the National Academy of Sciences 119(44):e2123415119. Full text via PubMed Central
- NHS Healthier Together. Healthy Sleep (Child 1–4 years): "Young toddlers may have two naps each day" changing to one nap of 1–3 hours; "By around 18 months old, most toddlers have one daytime nap." Healthy Sleep
- Baby Sleep Site. When Do Babies Drop to One Nap? 5 Signs, quoted for its opening concession that published figures range "anywhere from 10 months to 24 months old" and that "wide age ranges and contradictions make it hard for parents." Baby Sleep Site