18 Months vs 2T: How to Choose a Christmas Dress Size
Choosing a Christmas dress size gets confusing somewhere between her first and third birthday. Baby clothes are sized in months, toddler clothes in T sizes, and the two systems overlap right around age two. This guide covers 18 months vs 2T, 2T vs 3T, and what changes when the dress is for a December party with tights and a cardigan underneath.
How baby sizes and toddler sizes differ
Baby sizes are age ranges in months: 0–3, 3–6, 6–9, 9–12, 12–18 and 18–24 months. Toddler sizes are a number plus a T, which stands for toddler. The number is the age the size is made for, so 2T is for two-year-olds and 3T for three-year-olds.
The cut is different too. Baby clothes leave room for a diaper and tend to be a little shorter and rounder. Toddler clothes are made for a child who walks, so they usually run slightly longer and slimmer, with less room in the seat.
On our site, toddler sizes show the age in brackets, for example 2T (2Y), and sizes for older girls are written by age, like 6Y. Our baby Christmas dress sets come in month sizes up to 18–24 months. Our dresses go up to 9–12 months in month sizes, then continue with 1Y and the toddler sizes.
18 months vs 2T: which one to choose
An 18–24 months size and a 2T are made for children of about the same age, so her build and stage matter more than the number on the label.
- Pick 18–24 months if she is under two and still in diapers most of the day. It is also the safer choice for a girl who is small for her age.
- Pick 2T once she has turned two and walks everywhere, especially if she already wears 2T in other brands.
In a dress, length is what changes most between sizes. Compare the measurements in our size guide with a dress that fits her well right now.
In our shop, the Merry dress sets (dress, hat or bow, and shoes) go up to 18–24 months. They come in red plaid velvet, green smocked and Scottish tartan. If she is ready for a toddler dress, our Christmas dresses come in 1Y and 2T (2Y).
12 months vs 18 months
For a one-year-old, the choice is usually 12–18 months or 18–24 months in a dress set, or 1Y in a dress. Size for the age she will be on Christmas Day. A girl who turns one in October will be about 14 months old at Christmas, right in the middle of 12–18 months.
If she already fills out 12–18 months in November, the next size gives her room for a long-sleeve onesie or tights. For newborns and younger babies, see the size tips in our baby's first Christmas ideas.
2T vs 3T
Start with her age, then adjust. If she is tall for her age or her 2T clothes already feel snug, go up to 3T. If she just turned three and is petite, 2T may still fit well. Because our toddler sizes include the age, like 3T (3Y), you can check the label against her age at a glance. The same size rules apply to our toddler party dresses for birthdays, weddings and other parties all year.
What changes with a Christmas dress
A holiday dress is worn in winter, usually with tights and often with a cardigan, so the size you would pick for a summer dress can feel snug in December.
- Some of our dresses have short sleeves (the Josephine red velvet dress has flutter sleeves), so plan for a cardigan on cold days. The Merry baby sets have long sleeves.
- If you order in October, she has two more months to grow before she wears it.
- For a toddler who wants to walk and climb at a party, a hem around the knee is easier than one that brushes the floor.
- If she falls between two sizes, choose the larger one.
Quick size table by her age on Christmas Day
| Her age on Christmas Day | Baby dress sets | Dresses |
|---|---|---|
| 9 to 12 months | 9–12 months | 9–12 months |
| 12 to 18 months | 12–18 months | 1Y |
| 18 to 24 months | 18–24 months | 1Y or 2T (2Y), check the size guide |
| 2 years | Not available | 2T (2Y) |
| 3 years | Not available | 3T (3Y) |
| 4 years | Not available | 4T (4Y) |
| 5 years | Not available | 5T (5Y) |
Not every dress comes in every size. The size picker on each product page shows what is in stock that day.
When to order for Christmas
Orders ship the next business day from Lafayette, California, and arrive within 1–3 business days in the US. Order by December 17 for delivery before Christmas.
Ordering early also leaves time to fix a size. Unworn items with original tags can be returned within 30 days of delivery for store credit or an exchange. A $10 return shipping fee and a 5% restocking fee apply.
Frequently asked questions
Is 18 months the same as 2T?
No. They are made for children of a similar age, but 18–24 months is a baby size with room for a diaper, and 2T is a toddler size that is usually a little longer and slimmer.
Can a 2-year-old wear 18–24 months?
Often, yes, if she is small for her age or still in diapers. Check the length in the size guide before you order.
What size is 2T?
2T is the toddler size for two-year-olds. The T stands for toddler. On our dresses it is labeled 2T (2Y).
Should I size up for a Christmas dress?
If she is between sizes, yes. The extra room makes it easier to add tights and a cardigan, and she keeps growing between the day you order and Christmas.
Browse our toddler Christmas dresses from 1Y to 5T, or baby's first Christmas outfits from 0–3 to 18–24 months.