A typical 3-month-old weighs around 12.5 to 14 pounds, depending on sex. Boys at the 50th percentile weigh approximately 14 pounds, while girls at the 50th percentile come in closer to 12.5 pounds. But the “right” weight for your baby depends less on hitting a specific number and more on whether they’re growing consistently along their own curve.
Average Weight by Sex
The World Health Organization growth standards, which the CDC recommends for all children from birth to age 2, show a wide range of healthy weights at 3 months. A boy at the 5th percentile might weigh around 11 pounds, while one at the 95th percentile could be over 16 pounds. For girls, the 5th percentile sits near 10 pounds and the 95th around 15 pounds. All of those weights are considered normal.
That spread matters because parents often fixate on how their baby compares to the 50th percentile. Pediatricians care far more about your baby’s trajectory. A baby consistently tracking the 15th percentile is growing exactly as expected for them. A baby who was at the 75th percentile last month and dropped to the 25th this month is more concerning, even though both numbers are technically “normal.”
How Fast Babies Gain Weight at This Age
During the first few months, babies gain roughly 1 ounce per day, or about 5 to 7 ounces per week. That pace starts to slow around 4 months, dropping to about 20 grams (just under three-quarters of an ounce) per day. So at 3 months, your baby is still in the steeper part of their growth curve.
A common milestone to keep in mind: most babies double their birth weight by around 6 months. If your baby was born at 7 pounds, you’d expect them to be somewhere around 10 to 11 pounds by 3 months and approaching 14 pounds by 6 months. Babies born larger or smaller will follow different numbers, but the general doubling timeline holds.
Breastfed vs. Formula-Fed Patterns
Breastfed and formula-fed babies often grow at slightly different rates, and this is completely normal. Healthy breastfed infants typically put on weight more slowly than formula-fed infants during the first year, with the difference becoming more noticeable after about 3 months. Formula-fed babies tend to gain weight more quickly from that point forward.
This doesn’t mean breastfed babies are underfed. Their length growth tracks almost identically to formula-fed babies. The WHO growth charts were designed using breastfed infants as the standard, which is one reason the CDC recommends them for children under 2. If your pediatrician is using older CDC charts instead, a breastfed baby’s growth may look artificially slow.
The 3-Month Growth Spurt
Three months is one of the typical ages for an infant growth spurt, joining a list that includes 2 to 3 weeks, 6 weeks, 6 months, and 9 months. These spurts in babies tend to be short, often lasting up to three days. During one, you may notice your baby is hungrier than usual, fussier, or sleeping differently. Some babies want to nurse or take a bottle more frequently, while others seem irritable for no clear reason.
A growth spurt can temporarily make it seem like your baby isn’t getting enough to eat, especially if they’re breastfed and suddenly demanding more frequent feeds. This is normal and usually resolves within a few days as your milk supply adjusts to the increased demand.
Signs Your Baby Is Getting Enough
Weight checks happen at scheduled visits, but between appointments you can watch for daily indicators that your baby is well-nourished. The most reliable one: at least 6 heavy, wet diapers every 24 hours. Beyond that, a baby who is alert and responsive when awake, feeding with long rhythmic sucks and swallows, and settling after feeds is almost certainly getting what they need.
If you’re breastfeeding, pain-free feeding is another good sign. Your baby should have a wide latch with their chin touching your breast. You may feel a strong tug during the first few sucks, but ongoing pain usually signals a latch issue rather than a supply problem.
When Weight Drops Are a Concern
Pediatricians look for specific patterns that suggest a baby isn’t growing adequately. The clinical red flags include weight falling below the 5th percentile for age on two separate occasions, or a drop of more than two major percentile lines on the growth chart (for example, sliding from the 50th percentile to below the 10th). A single low reading at one visit isn’t usually cause for alarm, but a consistent downward trend warrants investigation.
Common causes of slow weight gain at this age include difficulty latching, insufficient milk transfer during breastfeeding, reflux, or food sensitivities. Most of these are manageable once identified. If your baby seems to be feeding well but isn’t gaining, a weighted feed (where the baby is weighed before and after nursing) can help pinpoint whether the issue is intake or something else.
Adjustments for Premature Babies
If your baby was born early, the number on the scale at 3 months of calendar age won’t match the charts the way it would for a full-term baby. Pediatricians use “corrected age” to account for prematurity: subtract the number of weeks your baby arrived early from their current age. A baby born at 34 weeks (6 weeks early) who is now 3 months old has a corrected age of about 6 weeks, and their weight should be compared to 6-week norms, not 3-month norms.
This correction is recommended for the first 2 years of life. It applies to developmental milestones as well, not just weight. So if your preemie seems small compared to other 3-month-olds, the corrected age comparison often tells a much more reassuring story.