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Normal baby weight by month

Updated November 21, 2016

Many factors affect infant weight gain including illness, metabolism, body shape, feeding methods and personality. Your baby's doctor will likely use a child centile chart for either a baby boy or baby girl from the Royal College of Paediatrics and Child Health to assess your infant's weight.

The first three months

Babies may drop between 5 and 10 percent of original weight after birth. Within two weeks, most infants gain the weight back. At one month, average baby weight is between 2.99 to 5 kilos (6.6 to 11.2 lbs). At three months, normal baby weight ranges between 4.3 and 6.9 kilos (9.5 to 15.4 lbs).

4 to 6 months old

Babies should gain 450 to 900 grams (1 to 2 lbs) monthly the first six months. Weight should range between 4.9 and 7.9 kilos (11 to 17.6 lbs.) at four months and 6.1 and 9.5 kilos (13.6 to 21.1 lbs.) by six months.

9 months old

The Royal College of Paediatrics and Child Health centile chart suggests a range of 7.5 to 10.5 kilos (15.6 to 24 lbs.) for 9-month-old infants. Growth rate averages about 455 grams (1 lb.) per month the first year.

12 months old

By 12 months old, a baby should weigh between 7.9 and 12.1 kilos (17.6 to 26.6 lbs.). Formula-fed babies will have gained, on average, 455 grams (1 lb.) more than their breast-fed peers the first year.

18 months old

An active baby will likely gain at a slower rate than her more laid-back counterpart. By 18 months old, babies should weigh between 9.1 and 13.9 kilos (20 and 30.6 lbs.).

24 months old

By 24 months of age, normal baby weight is between 10 and 15.5 kilos (22 to 34.1 lbs.) and should represent nearly four times his birth weight.

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About the Author

Lori Weaver is an experienced online writer and editor. She frequently contributes to a number of sites and covers a range of subject areas, including automotive trends, finance, marketing, sustainable living, renewable energy, healthcare, agriculture, real estate and other topics. She holds a degree in journalism from the University of Wisconsin, Madison.