What’s a Normal Baby Weight?

The moment your baby arrives, everyone wants to know: How much do they weigh? It's a natural question—weight is an easy number to hold onto in the blur of a new baby's first hours. But "normal" baby weight covers a surprisingly wide range, both before and after birth, and a healthy baby can land almost anywhere on that spectrum. Here's what the numbers actually mean, what shapes them, and which changes are worth a call to your pediatrician.

How much do babies weigh at birth?

Most full-term babies (37 to 40 weeks) weigh between 5 pounds, 8 ounces and 8 pounds, 13 ounces. The median birth weight is about 3.3 kilograms (7 pounds, 6 ounces) for boys and 3.2 kilograms (7 pounds, 2 ounces) for girls, according to the World Health Organization's Child Growth Standards—the reference data the CDC recommends U.S. pediatricians use to track growth in children under 2. Babies outside that range aren't automatically unhealthy, but they may get extra attention from the care team right after delivery just to be safe.

On medical charts, a baby's weight is compared to other babies born at the same gestational age. A baby whose weight lands in the expected middle range is considered appropriate for gestational age (AGA). Babies weighing less than 5 pounds, 8 ounces at birth are classified as low birth weight, and those under 3 pounds, 5 ounces are very low birth weight. Babies weighing more than 8 pounds, 13 ounces are often described as large for gestational age.

Fetal Weight Before Birth

During pregnancy, your healthcare provider estimates your baby's weight using ultrasound measurements and fundal height (the distance from your pubic bone to the top of your uterus). It's important to know upfront that these are estimates, not exact numbers, and can be off by a pound or more in either direction.

If an estimate consistently falls above the 90th percentile for gestational age, providers may use the term large for gestational age (LGA), sometimes also called fetal macrosomia. If an estimate falls below the 10th percentile, the term small for gestational age (SGA) may come up, which can sometimes—but not always—signal fetal growth restriction, a condition in which a baby isn't growing as expected in the womb.

But a prenatal size estimate isn't a guarantee of how your baby will look at birth. Plenty of babies predicted to be "big" or "small" arrive well within a typical range. If your provider raises a size concern during pregnancy, they'll typically recommend closer monitoring rather than treating the estimate as a fixed outcome. (Curious what these checkups look like? Here's what to expect at well-child visits.)

What factors affect a baby's birth weight?

A newborn's size is the product of many overlapping factors, most of which are out of anyone's control:

• Gestational age: Babies gain much of their weight in the final weeks of pregnancy, so babies born earlier than 37 weeks tend to weigh less, while those born past their due date tend to weigh more.
• Genetics and sex: Taller or larger-framed parents are more likely to have larger babies, and male newborns tend to weigh slightly more, on average, than female newborns.
• Maternal health conditions: Diabetes (including gestational diabetes) and obesity are linked to a higher chance of a larger baby—when diabetes isn't well managed during pregnancy, a fetus is more likely to develop larger shoulders and more body fat. Conditions that affect the placenta or maternal blood flow can restrict fetal growth instead.
• Multiples: Twins, triplets, and other multiples are typically smaller than singletons, since they share womb space and nutrient supply.
• Nutrition and substance exposure: Consistent, balanced nutrition supports steady fetal growth, while significant undernutrition or excessive pregnancy weight gain can shift a baby's size, and smoking or certain substances are linked to lower birth weight.

Because these factors interact, two babies born at the same gestational age to similarly built parents can land at very different points on the scale—and both can be perfectly healthy.

What’s a normal weight loss and gain after birth?

Almost every newborn loses weight in the first several days of life—which is totally expected. Babies are born carrying extra fluid, which they lose through urine and stool. In fact, one review found that healthy, full-term breastfed newborns lose an average of about 6% of their birth weight, with the second and third days after birth typically marking the lowest point.

From there, here's the general pattern pediatricians look for:

• By about 2 weeks: Most babies have regained their birth weight, and nearly all have by 3 weeks.
• First month: Babies typically gain close to an ounce (about 28 grams) per day.
• By about 6 months: Most babies have doubled their birth weight.
• By about 1 year: Most babies have tripled their birth weight.

Though growth isn't perfectly linear—expect bursts around 7 to 10 days, and again between 3 and 6 weeks, when your baby may seem suddenly ravenous. (That's a classic growth spurt, and it's totally normal, if exhausting.) Pediatricians track this progress using official growth charts. What matters most isn't hitting a specific percentile, it's a steady curve over time.

When to Call the Doctor About Weight Changes

Between well-child visits, you can gauge whether your baby is feeding well by tracking diapers: After the first several days, expect at least 5 to 6 wet diapers and several stools daily, plus a baby who generally seems satisfied after feedings. (Not sure how much your baby should be eating at each stage? Here's a full feeding schedule by age.)

Contact your pediatrician if you notice:

• Weight loss greater than 10% of birth weight in the newborn period
• Your baby hasn't regained their birth weight by 2 to 3 weeks of age
• Fewer than the expected number of wet or dirty diapers
• Your baby seems unusually sleepy, difficult to wake for feedings, or uninterested in eating
• Signs of dehydration, such as a dry mouth or a sunken soft spot
• A sudden drop or jump across growth chart percentiles, rather than a steady curve
• Your baby was born with a notably low or high birth weight, and you have questions about their catch-up growth plan

None of these signs are cause for panic, but they're worth a same-day or next-day call. Pediatricians would always rather field a check-in about feeding and weight than have a family wait it out at home.

The Bottom Line

"Normal" baby weight spans a wide, healthy range—both before and after birth. What your pediatrician cares about most isn't a single number on the scale, but a steady growth pattern over time, supported by good feeding and regular checkups. If a weigh-in ever surprises you, your baby's healthcare provider is the best resource for context and reassurance.

More on Baby Growth & Development:

• The Developmental Leap From 4 Days to 4 Months Old
• Your Baby’s Vision Development (and How to Spot Problems)
• When Do Babies Learn Object Permanence? (And Why It Matters)
• Baby Development Week-by-Week and Month-by-Month

• World Health Organization: Weight for Age Charts
• National Library of Medicine MedlinePlus: Appropriate for Gestational Age (AGA)
• Centers for Disease Control & Prevention: National Center for Health Statistics: Birthweight and Gestation
• NIH National Library of Medicine MedlinePlus: Large for Gestational Age (LGA)
• NIH National Library of Medicine MedlinePlus: Small for Gestational Age (SGA)
• NIH National Library of Medicine: Fetal Growth Restriction
• Mayo Clinic: Fetal Macrosomia: Symptoms & Causes
• Physiological Weight Loss in the Breastfed Neonate: A Systemic Review, Open Medicine, Oct 2008
• American Academy of Pediatrics: Your Baby’s First Month Growth & Physical Appearance
• American Academy of Pediatrics: Understanding Growth Charts: A Parent’s Guide to Percentiles & Z-Scores
• Centers for Disease Control & Prevention: Growth Charts

Disclaimer: The information on our site is NOT medical advice for any specific person or condition. It is only meant as general information. If you have any medical questions and concerns about your child or yourself, please contact your health provider.