Your Baby’s Developmental Milestones
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Your Baby’s Developmental Milestones

Monday, Apr 23, 2018

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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