Plan one easy-change outfit and a spare for a baby's first Christmas: a festive all-in-one, or a vest under a cardigan, under 3 months; a jumper over a vest from 6 months. Buy the age band that covers your baby on 25 December, or the later band for a jumper you want to last into January.
By the Babbez team · First-Christmas planning guide · Checked October 2026
Key takeaways
- Our Christmas-Age Map gives your baby's age on Christmas Day and on 31 January for every birth group from 26–31 Dec 2025 to 1–25 Dec 2026.
- In 5 of the 13 birth groups, every baby moves up a band by 31 January, so a jumper bought in the Christmas Day band may be short-lived.
- Save the Children's official date for Christmas Jumper Day 2026 is Thursday 10 December.
- Get the one-page December planner (PDF)
What should a baby wear on their first Christmas?
Think in layers plus a spare. The day brings visitors, a big meal, photos and probably a car journey, so the outfit has to survive a nappy change and a feed. Our picks by age:
- Under 3 months: a festive all-in-one with poppers down the front, or a vest under a soft knitted cardigan.
- 3 to 6 months: a vest with soft leggings or dungarees, plus a cardigan that comes off easily.
- 6 to 12 months: a jumper over a vest with soft trousers; dresses can ride up once a baby crawls.
- A toddler's second Christmas: a Christmas jumper with trousers, and a second top for the meal.
Whatever the age, pack one spare outfit and a bib for the meal and the car. The honest answer to “which outfit?” is that the poppers matter more than the pattern: you will change it at least once. Browsing for the day itself? See our baby clothing collection.
What size should you buy for your baby's first Christmas?
UK baby labels usually show an age band, and the Christmas-Age Map works out which band covers your baby on 25 December 2026 and again on 31 January 2027.
We count age in completed months from the date of birth, and a band covers a baby from its first age up to, but not including, its last. So a baby born on 25 March is 9 months old on Christmas Day, and one born on 31 October is 3 months old on 31 January:
| Born in | Age on 25 Dec | Band: 25 Dec → 31 Jan |
|---|---|---|
| 26–31 Dec 2025 | 11 months | 9–12 → 12–18 months |
| January 2026 | 10–11 months | 9–12 → 12–18 months |
| February 2026 | 9–10 months | 9–12 months (both) |
| March 2026 | 8–9 months | 6–9 or 9–12 → 9–12 months |
| April 2026 | 7–8 months | 6–9 → 9–12 months |
| May 2026 | 6–7 months | 6–9 months (both) |
| June 2026 | 5–6 months | 3–6 or 6–9 → 6–9 months |
We checked every birth date in each month, not only the first and last. Born in the second half of the year:
| Born in | Age on 25 Dec | Band: 25 Dec → 31 Jan |
|---|---|---|
| July 2026 | 4–5 months | 3–6 → 6–9 months |
| August 2026 | 3–4 months | 3–6 months (both) |
| September 2026 | 2–3 months | 0–3 or 3–6 → 3–6 months |
| October 2026 | 1–2 months | 0–3 → 3–6 months |
| November 2026 | 0–1 months | 0–3 months (both) |
| 1–25 Dec 2026 | 0–24 days | 0–3 months (both) |
Source: our arithmetic on bands written as 0–3, 3–6, 6–9, 9–12 and 12–18 months. The age is only the starting point: babies of the same age differ in size, shops size the same band differently, and many also sell smaller newborn sizes. If the label or the shop's chart gives a height (cm or inches) or weight (kg or lb), go by that; our UK baby grow size guide shows how.
Will a Christmas jumper still fit in January? The Turnover Rule
The last column of the map drives the Turnover Rule, which we use for jumpers and day outfits:
- Same band on both dates: buy that band.
- The band changes by 31 January: buy the later band for a jumper or day outfit you want to last into January, and turn the cuffs up on the day.
- Two bands on Christmas Day itself: go by the shop's chart for your baby's weight and length, not the age.
For an outfit worn on Christmas Day only, buy the band for 25 December. Across the map, in 5 of the 13 birth groups every baby moves up a band by 31 January; 3 sit on two bands on Christmas Day (babies born on the 26th or later also move up); 5 keep one band.
For example, for a baby born in July 2026, the band moves from 3–6 to 6–9 months.
The rule is for day clothes. For Christmas pyjamas, sleepsuits, baby grows and all-in-ones, go by the shop's chart for your baby now; for what to wear at night, see our UK guide to dressing a baby for sleep. Planning the whole winter wardrobe, not just Christmas? Our guide to buying baby clothes ahead covers the season.
When is Christmas Jumper Day 2026?
According to Save the Children, the official date for Christmas Jumper Day 2026 is Thursday 10 December. That is 15 days before Christmas Day, so one jumper can do both: size it with the map using the 25 December column.
For a toddler, look for a jumper with shoulder poppers or a wide neck, and check the care label, because it will be washed often.
How should you dress a baby indoors on Christmas Day?
Christmas often means a busy room, a car journey and then someone else's house. We don't set a temperature rule.
On its page about sudden infant death syndrome (SIDS), the NHS says: “Check your baby's temperature by feeling their chest or the back of their neck. Do not worry if their hands or feet feel cool, this is normal.” (Information from the NHS website, as at 211026).
The same NHS page lists, under “To reduce the risk of SIDS:”: “remove 1 or more layers of clothing or bedding if your baby skin is hot or sweating” (Information from the NHS website, as at 211026).
The same list (“To reduce the risk of SIDS:”) also says: “remove hats and extra clothing as soon as you come indoors or enter a car, bus or train even if it means waking your baby” (Information from the NHS website, as at 211026).
For more on dressing for naps and night-time, see our UK sleep dressing guide and the Lullaby Trust's cold weather page.
What are good first-Christmas keepsake and photo ideas?
Keepsakes cost little and last longest. Six we like:
- Handprints or footprints in ink on card, dated 25 December 2026.
- One photo in the same spot as your monthly photos, so Christmas sits in the series.
- Keep the outfit: wash it, add a tag with the date and the size, and store it.
- Ask each visitor to write one line to your baby in a notebook.
- Record 30 seconds of the room on Christmas morning: voices age well.
- Save the first Christmas card with your baby's name and keep it with the outfit.
Already taking monthly photos? Our monthly baby photo planner keeps the same spot and framing. Looking for things to do together through December? Our Christmas activities for toddlers gives one idea a day.
A dated December 2026 plan
- Sunday 29 November: weigh and measure your baby, then pick sizes with the Christmas-Age Map
- Thursday 10 December: Christmas Jumper Day (Save the Children's official date)
- Saturday 19 and Sunday 20 December: first-Christmas photos in daylight, before the visiting starts
- Thursday 24 December: lay out the outfit, the spare and the bib
- Friday 25 December: Christmas Day, a bank holiday in England and Wales, Scotland and Northern Ireland (gov.uk)
- Monday 28 December: Boxing Day bank holiday (substitute day) in all three, per the gov.uk bank holidays list
- Friday 1 January 2027: New Year’s Day bank holiday in all three (gov.uk); in Scotland, Monday 4 January is the 2nd January substitute day
- Sunday 31 January 2027: wash and store the outfit with its tag; the map's January check
Download the printable December planner (PDF)
One A4 page: the Christmas-Age Map, the Turnover Rule and this plan.
Frequently asked questions
What should a newborn wear on Christmas Day?
Our pick for under 3 months is a festive all-in-one with poppers down the front, or a vest under a soft knitted cardigan, plus a spare. A baby born 1–25 Dec 2026 is 0–24 days old on the day; the smallest labels vary by shop, so go by weight.
What size should a baby born in September wear at Christmas?
Born in September 2026, a baby is 2–3 months on 25 December and sits on 0–3 or 3–6 months, so go by the shop's chart for weight and length.
When is Christmas Jumper Day 2026?
Save the Children's official date is Thursday 10 December 2026.
Should a baby wear a hat indoors at Christmas?
The NHS says: “To reduce the risk of SIDS:” “remove hats and extra clothing as soon as you come indoors or enter a car, bus or train even if it means waking your baby” (Information from the NHS website, as at 211026).
Sources: gov.uk (UK bank holidays, England and Wales, Scotland and Northern Ireland tables, read October 2026); NHS (Sudden infant death syndrome (SIDS), last reviewed 25 November 2025); Save the Children (Christmas Jumper Day: the official 2026 date only). The Lullaby Trust page is linked for further reading. We checked every quote and date against its source page.
Contains public sector information licensed under the Open Government Licence v3.0. Each NHS line is marked "Information from the NHS website" with the date we copied it. Information from the NHS website is licensed under the Open Government Licence v3.0.
Use of NHS, gov.uk or Save the Children information, including links, does not imply their endorsement of Babbez. The map, the Turnover Rule, the outfit and keepsake ideas and the plan are Babbez's own (editorial standards). General information, not medical or safety advice; see our content disclaimer and medical disclaimer.