Understanding How Babies Gain Weight Each Month

Genetics, feeding habits, and whether a baby is breastfed or formula-fed all play a role in the weight gain of babies. Here are some milestones to keep in mind.

Babies come in various shapes and sizes, impacting how much weight they gain monthly. Factors like genetics, feeding frequency, and type of feeding (breast milk, formula, or a mix) can influence this.

According to the CDC, babies exclusively breastfed tend to gain weight quicker during the initial two months compared to formula-fed babies. However, breastfed infants may grow at a slower pace than formula-fed babies after the first year.

While there is a wide range of what is considered “normal,” there are rough guidelines available to help monitor your baby’s growth. Here, we outline typical patterns of weight gain per month from birth up to age 2 for your reference.

Birth to 3 Months Weight Gain

It may come as a surprise that newborns typically lose a few ounces of weight by day 2 or 3 after birth due to extra fluid they are born with. However, this initial weight loss is normal.

Following this initial loss, newborns generally gain around 1 ounce per day. Approximately half of newborns will reach or surpass their birth weight by day 9 or 10. By the second week, 76–86% of newborns will have regained their birth weight, and by the third week, 92–95% will be back to their birth weight.2

The majority of babies will typically gain between 4.5 to 6 pounds by the age of 3 months, with a monthly growth of up to 2 pounds and 1 to 1.5 inches in length during the first four months of their life.

4 Months to 1 Year Weight Gain

During the initial months of their first year, babies gradually develop the delightful “chub” associated with healthy infant growth. They will become more adept at latching and nursing or bottle-feeding and eventually transition to enjoying solid foods.

Typically, infants will double their birth weight by 4 or 5 months and triple it by the time they reach 1 year old.

1 to 2 Years Weight Gain

As your baby’s activity level increases, their chubby baby rolls will be replaced by developing muscle, although growth in the second year is not as rapid as in their first year.

Between their first and second birthdays, most toddlers will gain around 5 more pounds and add another 4 to 5 inches in height. By age 2, most toddlers will reach about half of their eventual adult height and 90% of their future adult head size.

Tracking Your Baby’s Growth Over Time

It is crucial to focus on the overall trend of your baby’s growth rather than just their monthly weight gain. During each well visit, The Positive Parent’s health care provider will monitor their child’s weight, height, and head circumference using a growth chart developed by the World Health Organization (WHO).

This standardized chart is based on data from national surveys, allowing health care providers to plot a growth curve and assess the baby’s growth in comparison to other same-age and same-sex babies.

While some Positive Parents may be concerned if their baby’s measurements fall on the extreme ends of the chart, it’s important to understand that the percentile ranking is not as critical as consistent growth. If the health care provider is not worried about the child’s size or growth patterns, then The Positive Parent can also relax about it.