Guide to Understanding Baby Clothing Sizes

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Guide to Understanding Infant & Toddler Clothing Sizes

Tip #10: Favor the Brands that Use Size Charts

A conscientious manufacturer knows that it’s hard enough to buy clothes for children without the additional challenge of having to guess if the item will even fit.

Whenever possible, stick with the brands that use size charts to translate each size into a weight and height range. As long as you have an idea of your child’s size, you’ll know right away if that romper marked “0-3” months will indeed fit your 2 month old.

Tip #9: The Labeled Size is the Maximum Size When No Age Range is Listed

Up until the age of 24 months, if an item is labeled “12 months” or “18 months” without an age range, translate it to mean “9-12” or “12-18” months. A size chart is always more accurate than an age range in determining the best fit for your child, but when there is no size chart, or even an age range, always select one size up from your child’s current age.

Translate sizes into ranges like this:

SIZE ON LABEL (months)    AGE (months)
Newborn                            0
3                                       0-3
6                                       3-6
9                                       6-9
12                                     9-12
18                                     12-18
24                                     18-24 

Tip #8: Swimwear Almost Always Runs Small

When buying a swimsuit for your child, always buy one or even two sizes up.

If your child normally wears clothing labeled 2T, buy a swimsuit labeled 3T. The only exception is with swim diapers that are labeled based on a child’s age and weight. They tend to be more accurate to a child’s true size. 

Tip #7: Sleepwear Usually Runs Small

When buying sleepwear that is designed to be snug-fitting, buy one size up.

In the United States , children’s sleepwear cannot be labeled as such unless the manufacturer meets fire safety requirements by making the clothing flame retardant and/or snug-fitting.

If you want your child’s sleepwear to be a bit loose, or if you have a younger child that is hard to dress in small armholes and necks, buy their sleepwear a size larger than their regular clothing.

Tip #6: Boutique Clothing Tends to Run Small

When buying clothing with sophisticated embellishments and stitching, unless a size chart is provided, buy one size up, especially in the infant sizes that have smaller ranges than the toddler sizes.

Keep in mind that boutique designs frequently require special care, such as hand-washing or cold water washing and line drying, and can shrink or be damaged when washed and dried by machine.


Tip #3: “4T” is Different From “4”

The overlap between Toddler (2T, 3T, 4T, 5T) and Child (2, 3, 4, 5, 6) sizes is a little confusing, particularly because different brands have different criteria for distinguishing between the two size types:

- Some Toddler sizes are roomier in the bottom to accommodate diapers

- Some Child sizes are narrower and longer (Size charts will indicate this by showing a similar weight range but larger height range than the corresponding Toddler size)

- Some Child sizes are the exact same size as their Toddler counterparts, but have a different cut and style


Most manufacturers group their clothing into the following age ranges:



3 m/0-3 m
6 m/3-6 m
9 m/6-9 m
12 m/9-12 m

18 m/12-18 m
24 m/18-24 m






6X (for girls)
7 (for boys)


Tip #2: European Sizing is Simple and Accurate

European sizing is based on children's height, so if you know your child’s height and can convert it from inches to centimeters, you will always know exactly which size to buy.

The following chart converts inches to centimeters and lists the corresponding European size. It also shows the U.S. age ranges to give you a familiar point of reference. 

10-18             25-46               n/a                      Preemie
18-22             46-56               56                       NB-3 m
22-24             56-61               62                       3-6 m
24-25             61-64               68                       6-9 m
26-30             66-76               74                       9-12 m
30-33             76-84               80                       12-18 m
32-35             81-89               86                       18-24 m
35-37             89-94               92                       2
37-40             94-102             98                       3
39-43             99-109             104                     3-4
43-48             109-122           110-116               5-6

Tip #1: “General” Size Charts are Guidelines Only

Most stores provide a general size chart to help as a guideline, but each brand may still use its own measurements for sizing their own clothing. Always look for a brand-specific size chart, or see if the item description includes its measurements.

General Size Chart

AGE             SIZE            WEIGHT (lbs)         HEIGHT (in)
Preemie       Preemie        Up to 6                  Up to 17
0 m             Newborn       Up to 9                  Up to 21
0-3 m          3 m              Up to 12                Up to 23
3-6 m          6 m              12-16                    24-26
6-9 m          9 m              16-18                    27-28
9-12 m        12 m            18-20                    28-30
12-18 m      18 m            20-24                    30-32
18-24 m      24 m            25-27*                  33-34*

AGE           SIZE           WEIGHT (lbs)        HEIGHT (in)       CHEST (in)      WAIST (in)     HIPS (in)
2               2T               25-27*                 33-35*               20                  20                 21
3               3T               28-32                   35-37                 21                  20½              22
4               4T               33-36*                 37-40*               22                  21                 23
5               5T               37-42*                 41-43*               23                  21½               24

AGE           SIZE           WEIGHT (lbs)        HEIGHT (in)       CHEST (in)      WAIST (in)     HIPS (in)
4                4                33-36*                 39-42*               22                 21                  23
5                5                37-42*                 42-44*               23                 21 ½              24
6                6                43-48                   44-46                 24                 22                 25
6                6X/7           49-54                   47-48                 25                 22 ½              26

* 18-24 months and 2T have the same weight range, but 2T has a greater height range.
* 4T and 4 have the same weight range, but 4 is taller by two inches.
* 5T and 5 have the same weight range, but a different height range.
The following manufacturers have provided weight and height size charts. Some also provide chest, waist, and hip measurements for children aged 2T to 6X.

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