What is the average baby weight by months?

Weight is one way to gauge a baby’s nutrition and physical development. It can be helpful, then, to know the average weight for babies month by month. First, it’s important to note that there is no such thing as a “normal” weight for babies.

Like adults, babies come in all shapes and sizes. If a baby’s weight is in the lower percentile, it doesn’t necessarily mean a problem with their growth or development. A weight chart can help a person track their baby’s growth in general terms.

The World Health Organization (WHO) weight chart is the most reliable source for determining the average weight of a baby month by month. The Centers for Disease Control and Prevention (CDC) recommend using this chart as a guide for babies up to 2 years of age.

There are various factors that can affect a baby’s weight, but on average, most babies will fall within the guidelines set by the WHO weight chart. If you are concerned about your baby’s weight, please consult with your pediatrician.

Average baby weights

According to the World Health Organization (WHO), the average weight of a full-term male baby is 7 pounds (lb) 6 ounces (oz), or 3.3 kilograms (kg). The average weight of a full-term female baby is 7 lb 2 oz or 3.2 kg.

The average weight of a baby born at 37–40 weeks gestation ranges from 5 lb 8 oz to 8 lb 13 oz, which is 2.5 to 4 kg.

At delivery, experts trusted Source considers a low birth weight to be less than 5 lb 8 oz, or 2.5 kg. A baby’s birth weight is commonly decreased by around 10% shortly after due to fluid loss; however, this is nothing to worry about as most babies gain the weight back within one week.

Baby weight chart by age.

It’s important to keep in mind that these numbers are just averages and don’t necessarily mean that any baby weighs too much or too little. The chart below shows baby weights in the 50th percentile. This is the average weight. Male babies tend to weigh a little more than female babies.

What to expect

Babies grow and gain weight quickly during the first six months of life. Although there is some variation, babies typically gain 4-7 ounces or 113-200 grams per week during the first four to six months.

Weight gain then slows slightly, with an average gain of 3-5 ounces (about 85-140 grams) per week between six and 18 months. On average, babies 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, while others may have a growth spurt which can happen at any time and cause a baby to move into a new weight percentile.

What affects baby weights

While weight is an important factor to consider when measuring physical development, it’s not the only indicator. Baby’s length and head circumference are also key measurements to take into account.

Doctors use all three measurements to get an idea about how the baby is developing, in comparison to other babies of the same age and gender. This gives them a more well-rounded picture of the baby’s growth.

It is also important to keep other developmental milestones in mind. Various checklists of milestones by age are available, including one from Pathways.org, which is endorsed by organizations such as the American Academy of Pediatrics 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 be involved, including:


Male newborns, on average, are born bigger and typically gain weight faster during infancy than female newborns.


Weight gain and growth rates in babies can depend on whether they consume breast milk or formula.

The American Academy of Pediatrics notes that, during the first 6 months, breastfed babies gain weight and grow faster than formula-fed babies.

However, that rate can shift during the next 6 months. From 6 months to 1 year, breastfed babies may gain weight and grow more slowly than formula-fed babies.

Medical Condition

Underlying health issues can cause a baby to gain weight more slowly. For example, babies with congenital heart irregularities may gain weight at a slower rate than babies without this condition.

Celiac disease is an example of a health issue that affects nutrient absorption or digestion and may lead to slow weight gain.


The average birth weight for full-term male babies is 7 lb 6 oz or 3.3 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 healthcare professionals track a baby’s physical development by comparing the weight of others of the same age and sex.

Although people often use percentile growth charts to compare their babies’ physical development against average weights by month, doctors usually assess steady growth, rather than a target percentile.

Additionally, even if a baby’s weight falls into a lower percentile, it will not necessarily be a small adult — just as longer babies do not necessarily become tall adults.

Percentile growth charts can give parents an idea about their babies’ physical development in relation to other babies of the same age, but doctors also look for other important indicators of development, such as length and head circumference.

Healthcare professionals always consider whether a baby is hitting other milestones on time. A detailed medical history can help rule out any medical conditions or nutritional deficiencies that may be impeding a baby’s weight gain.


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