Congratulations, you have a new little bean in your household! If your tiny one seems ravenous all the time, it’s because they are. Babies have a lot of growing and developing to do!

In the first 5 months of life, your baby will about double their birth weight. By the time they’re 1 year old, most babies triple their birth weight. But just like adults, babies come in all sizes and body types.

Some babies gain a lot of weight quickly. According to the World Health Organization’s (WHO) child growth standards, overall, boys gain weight faster than girls.

Squishiness and “rolls” can be normal and healthy for babies. Other babies might have leaner body types and appear thinner. This may also be completely normal.

Your pediatrician will weigh your baby regularly during well visits to make sure they’re within the range of normal weight gain for their length and age. It’s OK if your baby is off the charts sometimes — every baby is a little bit different and each gain weight at their own speed.

According to the Centers for Disease Control and Prevention (CDC), breastfed babies have a tiny head start in weight gain shortly after birth, but their overall weight gain in the first year is typically slower than formula-fed babies.

Still, up until age 2, physicians use the WHO growth charts as the standard growth curve for both breastfed and formula-fed babies.

In general, here’s what you can expect for your baby’s weight gain by week:

Baby’s ageAverage weight gain in ouncesAverage weight gain in grams
5 days to 4 months5–7 ounces per week170 grams per week
4 months to 6 months4–6 ounces per week113–150 grams per week
6 months to 12 months2–4 ounces per week57–113 grams per week

Breastfed babies

Generally, breastfed newborns gain weight faster than formula-fed babies for the first 3 months of life.

One likely reason for this is that breast milk is a dynamic and ever-changing food, composed of the exact nutrition a baby needs at that stage. On the other hand, formula is a static composition of ingredients.

For the same reason, the amount of pumped breast milk a baby receives in a bottle will sometimes differ than the amount of formula a baby of the same age receives.

When formula-fed babies need more calories, they must drink more at each feeding. Breast milk, however, will change in its composition and caloric content depending on the baby’s needs.

On average, breastfed babies drink around 800 milliliters (27 ounces) of milk per day in the first 6 months of life. As a rule of thumb, feed your breastfed baby on demand so they receive all the calories and nutrients they need.

How much breast milk should I put in a bottle?

A lot of breastfeeding parents returning to work want to know how much milk they should leave for their babies while they’re gone. If you’re planning to bottle-feed expressed milk, expect to give your baby about an ounce of milk per hour.

So, if you’re working an 8-hour day, for example, your baby might consume two 4-ounce bottles or three 3-ounce bottles during the time you’re gone.

Of course, this may depend on your baby’s age and how much they typically drink in a feeding. But in general, this will give you a baseline from which you can adjust to suit your baby’s needs.

Healthline

If you’re breastfeeding exclusively, you may need to track your baby’s weight a bit more carefully in the early weeks.

Weight gain is one way to determine how well breastfeeding is going — it’s not only a sign of how much milk you’re producing, but how well your baby is extracting the milk from the breast.

Formula-fed babies

Babies who are formula fed generally gain weight faster than breastfed babies after the first 3 months of life.

With formula feeding, it’s easier to know how much milk your baby is getting. You can tell how many ounces of formula your baby has finished by looking at their bottle.

But it’s also easier to accidentally overfeed your baby at times. This is because you’re more likely to keep feeding until the bottle is empty, even if your baby is already full. Sometimes momma’s eyes are bigger than baby’s stomach!

In fact, a 2016 study found that using a bigger bottle to feed formula to your baby can lead to faster weight gain in babies under 6 months old.

The researchers checked the weight of 386 two-month old babies. They found that babies who were fed with bottles 6 ounces or bigger were about 0.21 kilograms heavier than babies fed with smaller bottles.

This is kind of like adults eating from a smaller plate to feel fuller faster and avoid overeating!

Almost all babies lose some weight in the first week after birth. Don’t worry, though. As long as they’re feeding appropriately, they will quickly make up for it in coming weeks.

Most babies lose an average of 7 to 10 percent of their birth weight in the first few days. Ideally, they should be back to their birth weight by 10–14 days after birth. If not, be sure to speak with your pediatrician and possibly a lactation consultant to see if there are underlying problems with feeding.

If you experience breastfeeding challenges in the first few days after birth, you’re completely normal! Breastfeeding is often more complex than new parents expect.

Seek the help of a lactation consultant if you’re experiencing any of the following:

  • your baby doesn’t latch on deep enough, or it’s painful for mama
  • suckling seems weak during breastfeeding
  • baby’s urine is dark yellow
  • there’s red-brown “dust” in your baby’s diaper
  • you hear clicking or gagging when baby is drinking
  • your baby doesn’t have at least 2 to 4 poopy diapers a day
  • your baby is extra sleepy at the breast or has low energy
  • baby has a weak cry
  • your baby looks a bit yellow or has other signs of jaundice
  • there are other signs of dehydration in your baby

Weighing your baby regularly — at home or at your doctor’s office — is important because any amount of healthy weight gain is a sign that your baby is feeding well.

If your newborn hasn’t gained back their birth weight by day 10 to 14, has lost too much weight, or growth is too slow, your pediatrician, often along with a lactation consultant, can help.

And, if you find you need to supplement with formula, don’t stress! You’re not alone.

Breastfeeding offers numerous benefits, and your baby will still take advantage of them no matter how much breast milk they receive.

Babies gain weight and grow quickly in their first year. But weight gain can happen at different speeds and ranges for each little one.

Your baby’s weight gain depends on a lot of things, including genetics, how active they are, and whether you’re breastfeeding, formula feeding, or both.

Use the right growth chart and weighing methods to track your baby’s growth.

Don’t worry if your baby’s growth curve looks a little different than average. Talk to your doctor if you’re concerned, but as long as your baby is consistently gaining weight at their own pace, they’re doing just fine.