Average Infant Growth From Birth to One Year

Height and Weight Through the First Year With Charts

Hispanic baby girl sitting on a scale
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Like many parents, you might be wondering if your baby is growing normally. However, despite the temptation, it's not recommended to compare your child's growth and development to other children. Every child is an individual and grows at his or her own pace. Some kids are big, and some kids are small. There's definitely a range of healthy growth. And, since growth depends on many factors, not everyone follows the same pattern.

Here are some of the averages for weight and height during the first year. But, remember, if your child is a little smaller or bigger than these average measurements, it doesn't mean it isn't normal. 

What Growth Charts Mean

Growth charts and percentiles are just tools that help track the growth of children over time. The 50th percentile doesn't mean normal. The 50th percentile means average. While some children fall on the average line, many children fall below or above it. So, if your baby is not in the 50th percentile, it certainly doesn't mean that he or she is not growing at a healthy rate. Many factors contribute to your baby's height and weight, including genetics, diet, and activity level. Healthy infants are in the 5th percentile as well as the 95th percentile. 

WHO and CDC Growth Charts

All growth charts are not the same. The Centers for Disease Control and Prevention (CDC) provide a set of growth charts that include older data and information from a combination of feeding methods.

The CDC growth charts are a reference and show how children grew during a specific period in the United States. The World Health Organization (WHO) growth charts contain more data from breastfed babies. Since mothers are breastfeeding more and more and the WHO charts are considered a standard on how children should grow, the CDC recommends using the WHO growth charts for all babies - whether they are breastfeeding or taking formula - during the first two years.

The American Academy of Pediatrics (APP) agrees with the CDC recommendation. 

Average Newborn Weight

The average weight of a newborn is around 7 to 7 1/2 pounds (3.2 -3.4 kg). But, most full-term healthy newborns weigh anywhere from 5 pounds 11 ounces to 8 pounds 6 ounces (2.6 - 3.8 kg). Low birth weight is less than 5 pounds 8 ounces (2.5 kg) at full-term, and larger than average is a birthweight over 8 pounds 13 ounces (4.0 kg).

Many things can affect a newborn's birthweight. They include: 

  • How many weeks a pregnancy lasts: Babies born prematurely are typically smaller, and babies born past their due date may be larger.
  • Smoking: Mothers who smoke tend to have smaller babies.
  • Gestational diabetes: Diabetes during pregnancy can lead to a larger-than-average baby.
  • Nutritional status: Poor nutrition during pregnancy can lead to a smaller baby where excessive weight gain can lead to a larger baby.
  • Family history: Some babies are born smaller or larger, and it may just run in the family.
  • Gender: On average, newborn baby girls weight a little less than boys.
  • A multiple pregnancy: A single baby will likely have a greater birthweight than siblings born at the same time such as twins, triplets, or more. 

    During the first few days of life, it's normal for both breastfed and bottle-fed newborns to lose weight. A bottle-fed baby may lose up to 5 percent of his body weight, and an exclusively breastfed newborn can lose up to 10 percent. But, within two weeks, most newborns regain all the weight they have lost and return to their birth weight.

    Average Baby Weight By Month

    By one month, most infants will gain about a pound over their birth weight. At this age, infants are not as sleepy, they begin developing a regular feeding pattern, and they have a stronger suck during feedings.

    On average, babies gain about one pound each month for the first six months.

    Then, between six months and one year, weight gain slows down a little. Most babies double their birth weight by five to six months of age and triple it by the time they are a year old. 

    The average weight at six months is about 16 pounds 2 ounces (7.3 kg) for girls and 17 pounds 8 ounces (7.9 kg) for boys. By one year, the average weight of a baby girl is approximately 19 pounds 10 ounces (8.9 kg) with boys weighing about 21 pounds 3 ounces (9.6 kg). 

    Things that affect an infant's weight are: 

    • Gender: Boys tend to weigh slightly more than girls of the same age during infancy.
    • Type of Feeding: Breastfed babies may not gain weight as fast as babies who take formula. 
    • Activity Level: A more active infant may weigh less. 

    The two charts below show the average weight of babies from one month to one year based on the WHO growth charts. One table is for boys, and the other is for girls. Each chart shows the 50th percentile along with a range from the 3rd to the 97th percentile. These growth charts are for healthy, full-term infants. A doctor may use specialized growth charts for premature babies, or babies born with special health needs. Remember, this is just a reference. If you have concerns that your child is gaining too much weight or not enough, you should contact the doctor. 

    Average Baby Weight - Boys
           Age       50th Percentile         Range - 3rd to 97th Percentile
      1 month   9 lbs 14 oz  (4.5 kg)  7 lbs   8 oz - 12 lbs   9 oz  (3.4 - 5.7 kg)
      2 months 12 lbs   5 oz  (5.6 kg)  9 lbs 11 oz - 15 lbs   7 oz  (4.4 - 7.0 kg)
      3 months 14 lbs            (6.4 kg)11 lbs   3 oz - 17 lbs   8 oz  (5.1 - 7.9 kg)
      4 months 15 lbs   7 oz  (7.0 kg)12 lbs   6 oz - 18 lbs 15 oz  (5.6 - 8.6 kg)
      5 months 16 lbs   9 oz  (7.5 kg)13 lbs   6 oz - 20 lbs   5 oz  (6.1 - 9.2 kg)
      6 months 17 lbs   8 oz  (7.9 kg)14 lbs   3 oz - 21 lbs   7 oz  (6.4 - 9.7 kg)
      7 months 18 lbs   5 oz  (8.3 kg)14 lbs 14 oz - 22 lbs   6 oz  (6.7 - 10.2 kg)
      8 months 19 lbs            (8.6 kg)15 lbs   7 oz - 23 lbs   2 oz  (7.0 - 10.5 kg)
      9 months 19 lbs 10 oz  (8.9 kg)15 lbs 14 oz - 24 lbs   1 oz  (7.2 - 10.9 kg)
    10 months 20 lbs   3 oz  (9.2 kg)16 lbs   7 oz - 24 lbs 12 oz  (7.5 - 11.2 kg)
    11 months 20 lbs 12 oz  (9.4 kg)16 lbs 14 oz - 25 lbs   7 oz  (7.7 - 11.5 kg)
    12 months 21 lbs   3 oz  (9.6 kg) 17 lbs   5 oz - 26 lbs   2 oz  (7.8 - 11.8 kg)  

     

    Average Baby Weight - Girls
           Age      50th Percentile         Range - 3rd to 97th Percentile
       1 month   9 lbs   4 oz   (4.2 kg)   7 lbs   2 oz - 12 lbs             (3.2 - 5.4 kg)
       2 months 11 lbs   4 oz   (5.1 kg)   8 lbs 13 oz - 14 lbs   6 oz   (4.0 - 6.5 kg)
       3 months 12 lbs 14 oz   (5.8 kg 10 lbs   2 oz - 16 lbs   5 oz   (4.6 - 7.4 kg)
       4 months 14 lbs   2 oz   (6.4 kg) 11 lbs   3 oz - 17 lbs 14 oz   (5.1 - 8.1 kg)
       5 months 15 lbs   3 oz   (6.9 kg) 12 lbs   1 oz - 19 lbs   3 oz   (5.5 - 8.7 kg)
       6 months 16 lbs   2 oz   (7.3 kg) 12 lbs 13 oz - 20 lbs   5 oz   (5.8 - 9.2 kg)
       7 months 16 lbs 14 oz   (7.6 kg) 13 lbs   7 oz - 21 lbs   4 oz   (6.1 - 9.6 kg)
       8 months 17 lbs   7 oz   (7.9 kg) 13 lbs 14 oz - 22 lbs   2 oz   (6.3 - 10.0 kg)
       9 months 18 lbs   2 oz   (8.2 kg) 14 lbs   8 oz - 22 lbs 15 oz   (6.6 - 10.4 kg)
     10 months 18 lbs 11 oz   (8.5 kg) 14 lbs 15 oz - 23 lbs 10 oz   (6.8 - 10.7 kg)
     11 months 19 lbs   4 oz   (8.7 kg) 15 lbs   5 oz - 24 lbs   5 oz   (7.0 - 11.0 kg)
     12 months 19 lbs 10 oz   (8.9 kg) 15 lbs 12 oz - 25 lbs             (7.1 - 11.3 kg)

    ​​

    Average Baby Length (Height) By Month 

    In general, during the first six months, a baby grows about one inch per month. Between six months and one year, it slows down a bit to about a 1/2 inch per month. The average length of a baby boy at six months is approximately 26 1/2 inches (67.6 cm), and a baby girl is about 25 3/4 inches (65.7 cm). At one year boys are around 29 3/4 inches (75.7 cm), and girls average 29 inches (74 cm).

    The factors that determine height are: 

    • Genetics: The height of a child's mother, father, and other family members have the most significant impact on how tall the child will be.
    • Gender: Boys tend to be taller than girls.
    • Nutrition: Good nutrition for both mom during pregnancy and the baby after birth can ensure that the baby's body is getting the proper vitamins, minerals, and protein for healthy bones and optimal growth.
    • Sleep pattern: Studies show that infants grow in length after naps and long periods of sleep.
    • Physical activity: Body movement and physical activity help build strong muscles and bones. 
    • Overall health: Chronic illness and disease during childhood can affect growth and development.

    The two charts below show the average length or height of babies from one month to one year based on the WHO growth standards. One table is for boys, and the other is for girls. Each chart shows the 50th percentile along with a range from the 3rd to the 97th percentile. As mentioned above, these growth charts are for healthy, full-term infants. Again, this is just a reference. If you have concerns about your child's growth, you should contact your healthcare provider.

    *Inches are rounded to the nearest 1/4 inch. 

    Average Baby Length (Height) - Boys
          Age    50th Percentile   Range - 3rd to 97th Percentile
      1 month 21 1/2 in  (54.7 cm) 20       - 23        in  (51.1 - 58.4 cm)
      2 months 23       in  (58.4 cm) 21 1/2 - 24 1/2 in  (54.7 - 62.2 cm)
      3 months 24 1/4 in  (61.4 cm)  22 1/2 - 25 3/4 in  (57.6 -65.3 cm)
      4 months 25 1/4 in  (63.9 cm) 23 1/2 - 26 3/4 in  (60.0 - 67.8 cm)
      5 months 26       in  (65.9 cm)  24 1/2 - 27 1/2 in  (61.9 - 69.9 cm)
      6 months 26 1/2 in  (67.6 cm) 25       - 28 1/4 in  (63.6 - 71.6 cm)
      7 months 27 1/4 in  (69.2 cm) 25 1/2 - 28 3/4 in  (65.1 - 73.2 cm)
      8 months 27 3/4 in  (70.6 cm) 26 1/4 - 29 1/2 in  (66.5 - 74.7 cm)
      9 months 28 1/4 in  (72.0 cm) 26 3/4 - 30       in  (67.7 - 76.2 cm)
     10 months 28 3/4 in  (73.3 cm) 27 1/4 - 30 1/2 in  (69.0 - 77.6 cm)
     11 months  29 1/4 in  (74.5 cm) 27 1/2 - 31       in  (70.2 - 78.9 cm)
     12 months 29 3/4 in  (75.7 cm) 28       - 31 1/2 in  (71.3 - 80.2 cm)

     

    Average Baby Length (Height) - Girls
           Age    50th Percentile    Range - 3rd to 97th Percentile
       1 month 21       in  (53. 7 cm) 19 3/4 - 22 3/4 in (50.0 - 57.4 cm)
       2 months 22 1/2 in  (57.1 cm) 20 3/4 - 24 .     in (53.2 - 60.9 cm)
       3 months 23 1/2 in  (59.8 cm) 22       - 25       in (55.8 - 63.8 cm)
       4 months 24 1/2 in  (62.1 cm) 22 3/4 - 26       in (58.0 - 66.2 cm)
       5 months 25 1/4 in  (64.0 cm) 23 1/2 - 27       in (59.9 - 68.2 cm)
       6 months 25 3/4 in  (65.7 cm) 24 1/4 - 27 1/2 in (61.5 - 70.0 cm)
       7 months 26 1/2 in  (67.3 cm) 24 3/4 - 28 1/4 in (62.9 - 71.6 cm)
       8 months 27       in  (68.7 cm) 25 1/4 - 28 3/4 in (64.3 - 73.2 cm)
       9 months 27 1/2 in  (70.1 cm) 25 3/4 - 29 1/2 in (65.6 - 74.7 cm)
     10 months 28       in  (71.5 cm) 26 1/4 - 30 .     in (66.8 - 76.1 cm)
     11 months 28 1/2 in  (72.8 cm) 26 3/4 - 30 1/2 in (68.0 - 77.5 cm)
     12 months 29       in  (74.0 cm) 27 1/4 - 31 .     in (69.2 - 78.9 cm)

    Weight Loss and Gain in Babies

    While it is normal for a newborn to lose weight during the first few days of life, after that period, weight loss or poor weight gain in a child is a sign of a problem. For breastfed babies, it could mean that the baby is not getting enough breast milk.

    When it comes to weight gain, breastfed babies are less likely than formula-fed infants to gain too much weight too quickly. Breastfeeding may even help to prevent excessive weight gain and obesity. But, breastfed babies can gain too much if a mother has an overabundant supply of breast milk, the child spends too much time nursing, or solid foods are started early.

    Infant Growth Spurts

    Infants don't grow at a consistent rate. They have times when they grow slowly and times when they shoot up all of a sudden. When they have a big surge of growth in a short amount of time, it's called a growth spurt. Growth spurts can happen at any time, and they don't necessarily follow a pattern. Some of the ages that your child may experience a growth spurt are at ten days, three weeks, six weeks, three months, and six months.

    During and after a growth spurt, your baby will need more breast milk. Since breast milk is made based on supply and demand, your baby will breastfeed much more often during these times. You may need to breastfeed your baby as much as every hour or two. This increase in breastfeeding tells your body to make more milk. Luckily, these frequent feedings only last about a day or two as your milk supply adjusts to your growing baby's needs. After that, your child should settle back down into a more regular feeding routine.

    A Word from Verywell

    Children are individuals. They grow at different rates. It's difficult to compare one child to another, even if they are brothers and sisters. When you look around at other children, it can be scary if you think your child is smaller than he should be or he weighs more than he should for his age. Luckily, there is an easy way to ease your fears and find out for sure if your child is growing as expected. You just have to follow the regular schedule for well-child visits that your healthcare provider gives you.

    Your child's doctor is the best source of information when it comes to your child's growth and development. The doctor will weigh and measure your baby each time you see him. And, he will keep track of your little one's growth and overall health over time. This way, you can feel confident that your child is growing at a normal, healthy rate. And, if there are any issues or concerns, they can be noticed and taken care of right away. 

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