Your Baby’s Developmental Milestones

Lots of parents wonder whether their child is bigger or smaller than other kids the same age. (In the United States, the average baby weighs about 7½ pounds at birth.)

To give you a benchmark, here are the values from the 25th percentile to the 75th percentile for weight and height – meaning that half of kids fall within these ranges. A quarter of kids fall above these numbers and a quarter of kids below them.

Baby

Age Size Boys Girls
Birth Weight 6.7 – 8.1 pounds 6.5 – 7.8 pounds
Length 19.1 – 20.1 inches 18.9 – 19.8 inches
3 months Weight 13.0 – 15.2 pounds 11.8 – 14.0 pounds
Length 23.6 – 24.7 inches 23.0 – 24.1 inches

Quick tip: For babies born prematurely, use gestational age (not age since birth) when you look up their numbers in this chart.

6 months Weight 16.2 – 18.8 pounds 14.8 – 17.5 pounds
Length 26.1 – 27.2 inches 25.3 – 26.5 inches

Fast fact: By age 6 months, most babies have doubled their birth weight.

9 months Weight 18.2 – 21.1 pounds 16.7 – 19.7 pounds
Length 27.7 – 28.9 inches 27.0 – 28.3 inches
Growth charts and your baby’s first year

 Toddler

Age Size Boys Girls
12 months Weight 19.8 – 22.9 pounds 18.2 – 21.4 pounds
Height 29.2 – 30.5 inches 28.5 – 29.8 inches
15 months Weight 21.1 – 24.5 pounds 19.5 – 23.0 pounds
Height 30.5 – 31.8 inches 29.9 – 31.2 inches
18 months Weight 22.4 – 26.0 pounds 20.8 – 24.5 pounds
Height 31.7 – 33.1 inches 31.0 – 32.5 inches
21 months Weight 23.6 – 27.5 pounds 22.0 – 26.0 pounds
Height 32.7 – 34.3 inches 32.1 – 33.8 inches

Preschooler

Age Size Boys Girls
24 months Weight 24.8 – 28.9 pounds 23.3 – 27.5 pounds
Height 33.8 – 35.4 inches 33.2 – 34.9 inches
27 months Weight 27.0 – 31.2 pounds 25.8 – 30.0 pounds
Height 34.1 – 36.1 inches 33.7 – 35.6 inches
30 months Weight 27.8 – 32.2 pounds 26.7 – 31.1 pounds
Height 35.0 – 37.0 inches 34.6 – 36.6 inches
33 months Weight 28.6 – 33.2 pounds 27.6 – 32.3 pounds
Height 35.8 – 37.8 inches 35.4 – 37.4 inches
36 months Weight 29.5 – 34.3 pounds 28.4 – 33.4 pounds
Height 36.5 – 38.6 inches 36.0 – 38.1 inches
4 years Weight 33.3 – 39.1 pounds 32.2 – 38.5 pounds
Height 39.2 – 41.5 inches 38.6 – 41.0 inches

Big Kid

Age Size Boys Girls
5 years Weight 37.5 – 44.7 pounds 36.3 – 44.0 pounds
Height 41.7 – 44.2 inches 41.3 – 43.8 inches
6 years Weight 41.9 – 50.6 pounds 40.8 – 50.0 pounds
Height 44.2 – 46.9 inches 43.9 – 46.7 inches
7 years Weight 46.5 – 56.8 pounds 45.6 – 56.6 pounds
Height 46.6 – 49.5 inches 46.5 – 49.4 inches
8 years Weight 51.5 – 63.6 pounds 50.9 – 64.3 pounds
Height 48.9 – 52.0 inches 48.8 – 51.9 inches

 

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