A 5-month-old girl at the 50th percentile weighs about 15.2 pounds (6.9 kg), according to the WHO growth standards used in the United States for all children under 2. But “normal” spans a wide range. Girls between the 5th and 95th percentiles weigh anywhere from roughly 12.1 to 18.7 pounds at this age, and a baby tracking steadily along any percentile in that range is growing well.
The number on the scale matters less than the pattern over time. Your pediatrician plots your baby’s weight at each visit to see whether she’s following a consistent curve, not whether she hits one specific number.
What the Percentiles Mean
Growth percentiles compare your daughter to a large reference population of healthy infants. If she’s at the 30th percentile, that means 30% of girls her age weigh less and 70% weigh more. A baby at the 15th percentile is not underweight by default, and a baby at the 85th percentile is not overweight. Both are normal as long as they’re following their own curve without sudden drops or spikes.
The CDC recommends using the WHO international growth charts for all children under 24 months, regardless of whether they’re breastfed or formula-fed. These charts reflect how healthy infants grow under optimal conditions and are the standard in U.S. pediatric offices. After age 2, clinicians switch to CDC growth charts, which extend through age 19.
Weight becomes a clinical concern when it falls below the 2nd percentile for age and sex, or when a baby drops across two or more major percentile lines over a short period. A single weigh-in that looks low or high isn’t usually meaningful on its own.
Typical Weight Gain at This Age
Between 4 and 6 months, most babies gain about 1 to 1.25 pounds per month. That’s noticeably slower than the rapid gains of the first three months, when many infants put on closer to 1.5 to 2 pounds monthly. This gradual slowdown is completely normal and reflects the natural shift from explosive early growth to a more steady pace.
A common milestone parents hear about is doubling birth weight. This is widely quoted as happening between 5 and 6 months, though research shows the average is actually closer to 3.8 months (about 119 days). Girls tend to reach this milestone a bit later than boys, at around 129 days compared to 111 days. So if your 5-month-old daughter was born at 7 pounds and now weighs 14 pounds or more, she’s right on track. If she hasn’t quite doubled yet, that’s also fine, especially if she was breastfed or had a higher birth weight.
Breastfed vs. Formula-Fed Growth
Breastfed and formula-fed babies grow differently, and this becomes more visible right around the 5-month mark. Breastfed babies typically gain weight more slowly than formula-fed babies after about 3 months of age. This pattern continues even after solid foods are introduced, usually around 4 to 6 months. A breastfed girl who slides from the 50th to the 35th percentile during this period is often following a perfectly healthy trajectory.
Length growth, on the other hand, stays similar between both feeding types. So if your breastfed daughter seems leaner than a formula-fed baby the same age, that’s expected. The WHO growth charts were designed with breastfed infants as the biological norm, which is one reason the CDC recommends them for this age group.
If Your Baby Was Born Early
Premature babies need their age adjusted before you compare them to any growth chart. To calculate your daughter’s corrected age, subtract the number of weeks she was born early from her actual age. If she was born at 34 weeks (6 weeks early) and is now 5 months old by calendar age, her corrected age is closer to 3.5 months. You’d compare her weight to the 3.5-month mark on the growth chart, not the 5-month mark.
This adjustment matters for the first 2 years. Without it, a healthy preemie can look underweight or developmentally behind when she’s actually growing exactly as expected for her corrected age. Your pediatrician will track both ages at well-child visits.
When Weight Patterns Signal a Problem
Most variation in baby weight is normal. But certain patterns are worth paying attention to. Weight that falls below the 2nd percentile, or a sharp drop across percentile lines over two or more visits, can indicate that a baby isn’t getting enough nutrition or that an underlying condition is affecting growth. Similarly, weight-for-length above the 98th percentile may warrant a closer look.
Practical signs that often accompany genuine growth concerns include fewer than 4 wet diapers a day, persistent fussiness during or after feeds, and a baby who seems unusually lethargic. On their own, a few days of fussy eating or a weigh-in that seems lower than expected rarely point to a real problem. Growth is assessed over weeks and months, not single data points.
If your daughter is tracking along her own percentile line, gaining roughly a pound a month, producing plenty of wet diapers, and meeting developmental milestones, her weight is doing exactly what it should, whether she’s 13 pounds or 17.