Key takeaways
- Children develop at different paces, but the average birth weight of a full-term male baby is 3.3 kilograms (kg) and 3.2 kg for a female.
- Growth charts can provide a guide to the average weight of a baby. However, healthcare professionals will consider various measures when monitoring a baby’s growth, including length and head circumference.
- It is important to attend regular checkups with a pediatrician to monitor a baby’s growth and development during their first year.
First, it is worth noting that average weight is not typical weight. Just like adults, babies come in all shapes and sizes.
If a baby’s weight is in a lower percentile, this does not necessarily signal a problem with their growth or physical development. With this in mind, using a weight chart can help a person generally track their baby’s growth.
This article describes a baby’s average weight month by month from birth and explores what can affect it.
The
According to the WHO, the average birth weight of a full-term male baby is 7 pounds (lb) 6 ounces (oz), or 3.3 kilograms (kg). The average birth weight of a full-term female baby is 7 lb 2 oz, or 3.2 kg.
At delivery, experts consider a low birth weight to be less than
It is common for babies to lose some weight during the first week after birth. This decrease is mostly due to fluid loss and usually nothing to worry about. Most babies gain back this weight without any concerns.
Weight charts can help someone understand what percentile their baby’s weight falls into.
For example, if their weight is in the 60th percentile, 40% of babies of the same age and sex weigh more, and 60% of these babies weigh less.
This does not necessarily mean that any baby weighs too much or too little. It can simply indicate where a baby’s weight falls on a spectrum.
The chart below shows baby weights in the 50th percentile, which refers to the average weight.
| Baby age | Female 50th percentile weight | Male 50th percentile weight |
|---|---|---|
| Birth | 7 lb 2 oz (3.2 kg) | 7 lb 6 oz (3.3 kg) |
| 1 month | 9 lb 4 oz (4.2 kg) | 9 lb 14 oz (4.5 kg) |
| 2 months | 11 lb 5 oz (5.1 kg) | 12 lb 4 oz (5.6 kg) |
| 3 months | 12 lb 14 oz (5.8 kg) | 14 lb 1 oz (6.4 kg) |
| 4 months | 14 lb 3 oz (6.4 kg) | 15 lb 7 oz (7.0 kg) |
| 5 months | 15 lb 3 oz (6.9 kg) | 16 lb 9 oz (7.5 kg) |
| 6 months | 16 lb 1 oz (7.3 kg) | 17 lb 8 oz (7.9 kg) |
| 7 months | 16 lb 14 oz (7.6 kg) | 18 lb 5 oz (8.3 kg) |
| 8 months | 17 lb 8 oz (7.9 kg) | 18 lb 15 oz (8.6 kg) |
| 9 months | 18 lb 2 oz (8.2 kg) | 19 lb 10 oz (8.9 kg) |
| 10 months | 18 lb 11 oz (8.5 kg) | 20 lb 3 oz (9.2 kg) |
| 11 months | 19 lb 4 oz (8.7 kg) | 20 lb 12 oz (9.4 kg) |
| 12 months | 19 lb 12 oz (8.9 kg) | 21 lb 4 oz (9.6 kg) |
Babies usually gain weight most rapidly during the first 6 months of their life.
Typically, breastfed babies gain weight more slowly in their
It is common for babies to lose weight in their first week of life. They usually gain this weight back by the time they are 2 weeks old.
Although this can vary, babies tend to double their birth weight between the ages of 4 and 6 months and may weigh triple their birth weight by their first birthday.
However, growth patterns do not follow a clear schedule. Some babies gain weight steadily and stay in the same percentile, or close to it, for several months.
Others gain weight rapidly, signaling a growth spurt, which can occur at any time. This may move a baby into a new weight percentile.
It is important not to focus on weight as the only indicator of physical development. Other measurements of this development include the baby’s length and head circumference.
Considering all three measurements gives doctors an idea about how the baby is growing, compared with other babies of the same age and sex.
Meanwhile, it is also important to consider other developmental milestones. Various checklists of milestones by age are available, including one from Pathways.org, which has endorsement from organizations such as the American Academy of Pediatrics (AAP) and the National Association of Pediatric Nurse Practitioners.
For anyone looking for more information about what influences the weight of a baby, several factors can have a role, including the following.
Sex
Male newborns tend to be bigger than female newborns and typically gain weight a little faster during infancy.
Nutrition
Weight gain and growth rates can also depend on whether the baby consumes breast milk or formula.
Breastfed babies gain weight and grow
However, growth generally follows a similar trend for both chest or breastfed and formula-fed babies.
Weight continues to fluctuate even after the baby starts eating other foods.
Medical conditions
Underlying health issues can cause a baby to gain weight more slowly. For example, babies with congenital heart irregularities may gain weight at a
Health issues that affect nutrient absorption or digestion, such as celiac disease, may also lead to slow weight gain.
Prematurity
Babies born prematurely may weigh less during their first year than babies born at full term. However, they tend to grow parallel to the curve of growth charts.
It is important to attend regular checkups with a pediatrician in a baby’s early stages of life. During these checkups, the pediatrician will assess the baby’s growth and development to ensure everything is progressing as expected.
A pediatrician will advise how often they should see a baby, as it may vary from one baby to another.
It can be helpful to keep notes on a baby’s growth and development and bring these to your appointments for the pediatrician to review.
Parents or caregivers can talk with a pediatrician at these checkups if they have any concerns about the baby’s growth or development.
However, it may also be beneficial to speak with a pediatrician between checkups if there are any major concerns, particularly if a baby is no longer following the typical growth curve or is not eating as usual.
Generally, a baby will weigh double their initial birth weight by the age of 4 to 6 months. They will usually weigh triple their birth weight by 12 months.
The average birth weight for full-term male babies is 7 pounds (lb) 6 ounces (oz), or 3.3 kilograms (kg). For female babies born full-term, the average birth weight is 7 lb 2 oz, or 3.2 kg.
Baby weight charts can help a healthcare team track a baby’s physical development by comparing the baby’s weight with that of an infant of the same age and sex.
Still, a doctor usually looks for steady growth rather than a target percentile when assessing a baby’s physical development. Even if a baby’s weight is in a lower percentile, it will not necessarily lead to them developing into a small adult, just as longer babies do not necessarily become tall adults.