Baby clothing sizes in the US are labeled by age range in months — but age alone is a rough guide. Two babies of the same age can differ by several inches in length and several pounds in weight. For the most accurate fit, check the weight and height range printed on the garment's label, not just the age.
US baby clothing sizes
| US Label | Age (approx) | Weight (lbs) | Height (in) |
|---|---|---|---|
| Newborn (NB) | 0–1 month | up to 9 lbs | up to 21.5 in |
| 0–3M | 0–3 months | 8–12.5 lbs | 21.5–24 in |
| 3–6M | 3–6 months | 12.5–17 lbs | 24–26.5 in |
| 6–9M | 6–9 months | 17–21 lbs | 26.5–28.5 in |
| 9–12M | 9–12 months | 21–25 lbs | 28.5–30.5 in |
| 12–18M | 12–18 months | 25–28 lbs | 30.5–33 in |
| 18–24M | 18–24 months | 28–30 lbs | 33–35.5 in |
| 2T | 24–36 months | 27–32 lbs | 34–37 in |
| 3T | 36–48 months | 31–38 lbs | 37–41 in |
| 4T | 48–60 months | 38–44 lbs | 41–45 in |
US to EU and UK size conversion
European baby clothing sizes are based on body length in centimeters, not age.
| US Label | EU Size | UK Label |
|---|---|---|
| Newborn | 50–56 | Newborn / Up to 1 month |
| 0–3M | 62 | 0–3 months |
| 3–6M | 68 | 3–6 months |
| 6–9M | 74 | 6–9 months |
| 9–12M | 80 | 9–12 months |
| 12–18M | 86 | 12–18 months |
| 18–24M | 92 | 18–24 months |
| 2T | 92–98 | 2 years |
| 3T | 98–104 | 3 years |
| 4T | 104–110 | 4 years |
2T vs 24M — what is the difference?
24M and 2T cover approximately the same height and weight range, but they are cut differently:
- 24M is designed for babies still wearing diapers — roomier in the seat and crotch.
- 2T (toddler) is cut slimmer, assuming the child is potty training or trained.
If your toddler is still in diapers, 24M will usually fit more comfortably than 2T even if the weight/height overlaps.
Tips for buying ahead
Baby clothing makes popular gift items, which means babies often receive more newborn and 0–3M clothes than they will ever wear. If buying ahead:
- Skip NB entirely for larger babies. Many babies born above 8.5 lbs skip newborn size altogether.
- Buy the next size up, not the current one. Babies grow out of each size in 6–12 weeks.
- Check the season. A size labeled 6–9M for a baby born in September will be worn in late winter — buy accordingly.
Once your child starts walking, see the Kids Shoe Size Chart by Age → for a full reference covering US, UK, EU, and Japan sizes from first steps through age 10.