Sizing
Baby Clothes Size Chart
Baby clothes are sized by weight, not age — which is why the label on the front confuses almost everyone. Put in your baby's weight and see the size, how much growing room is left in it, and which brands will fit differently at the same number.
Read this first
What the label on the front actually means
Almost every sizing question comes down to one misunderstanding: the number on a baby garment is the end of a range, not the beginning. Every figure below is taken from the chart on this page, so you can check it against the bars yourself.
| The question | The answer, from the chart |
|---|---|
| Is 0-3M the same as 3 months? | No. 0-3M covers 8–12 lb and runs from birth to about three months. A garment marked "3M" on its own is the next size up in most US ranges. The trap is that "0-3M" is the only size that starts at zero — every other number is the start of its range. 3-6M begins at three months. 0-3M is the exception, and it catches everyone once. |
| Can a 7 lb baby wear 0-3 month clothes? | They will fit, but they are not in that size yet. 0-3M starts at 8 lb, and 7 lb sits inside Newborn (5–8 lb). In practice a 7 lb baby wears newborn for a few weeks and then moves up — which is why newborn clothes are worth buying in small numbers rather than in a bundle. |
| Does "6 months" mean 3-6 or 6-9? | On this chart the label is the range it covers: 3-6M is 12–16 lb, 6-9M is 16–20 lb. So "6 months" as a garment marking sits at the boundary — which is exactly why brands that print "6M" cause so much confusion. Weight settles it: under 16 lb, 3-6M; over 16 lb, 6-9M. |
| Is 2T the same as 24 months? | Nearly — and the difference is height, not weight. 18-24M is 28–32 lb at 32.5–34″; 2T is 29–32 lb at 34–36″. The weights overlap almost completely, but 2T is cut for a taller child. If your toddler is heavy but short, 24 months still fits better. |
These ranges are the standard baby-clothing sizes. Individual brands drift from them in either direction — that is what the brand scale in the tool above is for.
What size is my baby?
lb
in
months
Weight first. Baby clothes are sized by weight before anything else — a 12 lb baby is usually in 3-6M whether they are short or tall. Height refines it. Age is the least reliable of the three, which is the whole reason the labels confuse people.
Enter at least one
Weight is the best single number
Baby clothes are sized by weight first — a 12 lb baby is usually in 3-6M even if they are short or tall for their age. Height refines it; age is the least reliable of the three.
Every size, drawn to the same weight scale
Each bar is one size, positioned by the weight it covers. This is the bit a printed table cannot show you: a size ends where its bar ends. 0-3M stops at 12 lb — it is not "from three months", it is up to about three months, or 12 lb, whichever arrives first.
PreemiePremature0–5 lb
Newborn (NB)0-1 months5–8 lb
0-3M0-3 months8–12 lb
3-6M3-6 months12–16 lb
6-9M6-9 months16–20 lb
9-12M9-12 months20–24 lb
12-18M12-18 months24–28 lb
18-24M18-24 months28–32 lb
2T2 years29–32 lb
3T3 years32–35 lb
4T4 years35–39 lb
5T5 years39–45 lb
Do sizes vary by brand? Yes — by up to a full size
Same number on the label, different actual fit. Brands that run small sit left; brands that run large sit right. If your baby is between sizes, this is the difference between something that lasts and something that fits for a fortnight.
GerberRuns small
Zara BabyRuns small
Burt's Bees BabySlim fit
Carter'sTrue to size
Old NavyTrue to size
PrimaryTrue to size
Gap BabyTrue to size
Cat & Jack (Target)Slightly large
H&M BabyRuns large
Hanna AnderssonRuns large
- Carter's — True to size. Runs true to size or slightly large. Great for stockier babies. #1 selling baby clothing brand.
- Gerber — Runs small. Runs small, especially in length. Size up for longer babies. Budget-friendly basics.
- H&M Baby — Runs large. Uses European sizing, runs large. Great for growing into. Trendy designs.
- Old Navy — True to size. True to size with consistent fit. Good quality at affordable prices.
- Cat & Jack (Target) — Slightly large. Slightly generous sizing. Durable quality that holds up well to washing.
- Burt's Bees Baby — Slim fit. True to size with slim fit. Great for leaner babies. 100% organic cotton.
- Primary — True to size. True to size. No logos or graphics. High-quality basics in every color.
- Hanna Andersson — Runs large. European sizing, runs large. Premium quality, lasts through multiple kids.
- Gap Baby — True to size. True to size. Classic styles with good durability.
- Zara Baby — Runs small. European sizing but runs small. Fashion-forward designs.
| Size | Age | Weight | Height | Chest | |
|---|---|---|---|---|---|
| Preemie | Premature | 0–5 lb | 0–17″ | 10-11″ | Check Price |
| Newborn (NB) | 0-1 months | 5–8 lb | 17–21″ | 11-12″ | Check Price |
| 0-3M | 0-3 months | 8–12 lb | 21–24″ | 12-13″ | Check Price |
| 3-6M | 3-6 months | 12–16 lb | 24–26.5″ | 13-14″ | Check Price |
| 6-9M | 6-9 months | 16–20 lb | 26.5–28.5″ | 14-15″ | Check Price |
| 9-12M | 9-12 months | 20–24 lb | 28.5–30.5″ | 15-16″ | Check Price |
| 12-18M | 12-18 months | 24–28 lb | 30.5–32.5″ | 16-17″ | Check Price |
| 18-24M | 18-24 months | 28–32 lb | 32.5–34″ | 17-18″ | Check Price |
| 2T | 2 years | 29–32 lb | 34–36″ | 18-19″ | Check Price |
| 3T | 3 years | 32–35 lb | 36–39″ | 19-20″ | Check Price |
| 4T | 4 years | 35–39 lb | 39–42″ | 20-21″ | Check Price |
| 5T | 5 years | 39–45 lb | 42–45″ | 21-22″ | Check Price |
Practical
When to size up, and what to buy in advance
The chart tells you the boundaries. These are the rules of thumb that stop you buying the wrong quantity of the wrong size.
| Situation | What to do |
|---|---|
| Baby is between two sizes | Buy the larger one. A slightly baggy sleepsuit is comfortable; a tight one is not, and babies do not shrink. |
| Buying before the baby arrives | Weight is unknown, so buy small amounts of Newborn and 0-3M rather than a full wardrobe of either. Nobody can predict a birth weight. |
| Buying as a gift | Buy 3-6M or larger. Newborn is the size parents already have too much of, and a gift in 6-9M will still be worn in six months. |
| Brand runs small | Size up one. The brand scale above shows which ones — and for those, buying your baby's current size means buying something that fits for weeks rather than months. |
| Winter baby | Buy a size up for outerwear. Layers and bulky sleep sacks eat into the room inside a garment. |
Questions
Baby clothes sizing questions
What size is a 10 lb baby in baby clothes?
A 10 lb baby is in 0-3M, which on this chart covers 8–12 lb and roughly 21–24 inches. They have about 2 lb of growing room before moving to 3-6M. Enter the exact weight in the finder above and it will show you the size and the remaining room.
Do baby clothes sizes vary by brand?
Yes, by up to a full size. On this chart, Carter's, Old Navy, Gap Baby and Primary run true to size; Cat & Jack runs slightly generous; Gerber and Zara Baby run small, especially in length; H&M Baby and Hanna Andersson run large because they use European sizing; and Burt's Bees Baby is true to size but cut slim. The brand scale above plots each one.
Which brands of baby clothes run big?
H&M Baby and Hanna Andersson run the largest of the brands listed here — both use European sizing, so a garment marked 0-3M is cut more generously than the same size in a US brand. Cat & Jack (Target) runs slightly large as well.
How many baby clothes do I actually need?
Fewer than the lists suggest. Roughly 8–10 bodysuits, 6–8 sleepers and 5–6 pairs of socks per size will get you through a week between washes. The mistake is buying a full wardrobe in Newborn — most babies leave that size within a month.
Is 0-3 months the same as 3 months?
No. 0-3M covers 8–12 lb and runs from birth to about three months. A separate "3M" label usually denotes the next size up, which is why the two get mixed up. Weight is the reliable number: under 12 lb is 0-3M, over 12 lb is 3-6M.
How long will a size last?
That depends entirely on your baby, and no chart can predict it — which is why the finder shows how much weight range is left in the size rather than guessing at months. A size with 4 lb of room left will last considerably longer than one with 1 lb left.
Next
Where to go from here
Once the size question is settled, these are the three purchases worth getting right — and each answers a measurement question rather than repeating a top-ten list.