A 4-month-old girl at the 50th percentile weighs about 14.1 pounds (6.4 kg), meaning half of all girls her age weigh more and half weigh less. The normal range is wide: girls between the 5th and 95th percentiles weigh anywhere from 11 pounds (5.0 kg) to 17.6 pounds (8.0 kg). Where your baby falls within that range matters less than whether she’s growing consistently over time.
The Normal Weight Range at 4 Months
These numbers come from the WHO growth standards, which the CDC and the American Academy of Pediatrics recommend for all children under 2, regardless of whether they’re breastfed or formula-fed.
- 5th percentile: 11 pounds (5.0 kg)
- 50th percentile: 14.1 pounds (6.4 kg)
- 95th percentile: 17.6 pounds (8.0 kg)
A baby at the 15th percentile is just as healthy as one at the 85th. Percentiles describe where your baby sits relative to other babies her age, not whether something is wrong. What pediatricians watch for is the overall trajectory: a baby who has been tracking along the 25th percentile since birth and continues doing so is growing exactly as expected.
How Fast She Should Be Gaining
In the first three months of life, babies gain roughly 1 ounce per day. Around the 4-month mark, that pace naturally slows to about two-thirds of an ounce (20 grams) per day, or roughly 5 ounces per week. This slowdown is completely normal and catches many parents off guard, especially if they’ve been used to watching the numbers climb quickly on the scale.
A common milestone to keep in mind: most babies double their birth weight by 6 months. So if your daughter was born at 7 pounds, she’d be expected to reach about 14 pounds sometime between now and her 6-month checkup. If she’s already there at 4 months, that’s fine. If she’s not quite there yet, that’s also fine. The doubling guideline is a rough benchmark, not a deadline.
Breastfed vs. Formula-Fed Growth Patterns
Breastfed and formula-fed babies often follow slightly different weight curves, and this difference tends to become noticeable right around 3 to 4 months. Breastfed babies typically put on weight more slowly than formula-fed babies after the first few months. Formula-fed infants tend to gain weight faster from about 3 months onward, and this difference in weight patterns continues even after solid foods are introduced later.
Both patterns are normal. The WHO growth charts were built from data on breastfed infants, so a breastfed baby who tracks a bit lower than a formula-fed peer is following the expected curve. Length (height) growth, on the other hand, is similar between the two groups.
When a Percentile Shift Matters
Babies don’t always stay locked on one percentile line. Minor fluctuations between well-child visits are common, especially during growth spurts or illness. What raises concern is a sustained downward crossing of percentile lines. For example, a baby who was tracking along the 75th percentile and drops to the 25th over two or three visits may need a closer look, even if her current weight still falls within the “normal” range.
The absolute number on the scale matters less than the pattern. A small baby who grows steadily along the 10th percentile is generally healthier than a larger baby whose curve is dropping. Your pediatrician plots your daughter’s weight at every visit specifically to catch these trends early, which is one reason those frequent checkups in the first year are so important.
Physical Development at 4 Months
Weight is just one piece of the growth picture. At 4 months, healthy development shows up in movement and coordination too. By this age, most babies can hold their head steady without support when being held upright, push up onto their elbows during tummy time, swing their arms at toys, bring their hands to their mouth, and hold a toy placed in their hand. These motor milestones tend to emerge alongside healthy weight gain and can be just as reassuring as the number on the scale.
If your daughter is hitting these milestones, feeding well, producing plenty of wet diapers, and staying on a consistent growth curve, her weight is very likely right where it should be, whether she’s 12 pounds or 16.