Understanding baby size
A baby’s length is measured from the top of their head to the bottom of one of their heels. It’s the same as their height, but height is measured standing up, whereas length is measured while your baby is lying down.
The average length at birth for a full-term baby is 19 to 20 inches (about 50 cm). But the range for most newborns is between 18 and 22 inches (45.7 to 60 cm).
If your newborn baby is in the 50th (middle) percentile, that means 50 percent of newborn babies measure shorter than your baby, and 50 percent of newborn babies measure longer.
|Age||50th percentile length for male babies||50th percentile length for female babies|
|Birth||19.75 in (49.9 cm)||19.25 in (49.1 cm)|
|1 month||21.5 in (54.7 cm)||21.25 in (53.7 cm)|
|2 months||23 in (58.4 cm)||22.5 in (57.1 cm)|
|3 months||24.25 in (61.4 cm)||23.25 in (59.8 cm)|
|4 months||25 in (63.9 cm)||24.25 in (62.1 cm)|
|5 months||26 in (65.9 cm)||25.25 in (64 cm)|
|6 months||26.5 in (67.6 cm)||25.75 in (65.7 cm)|
|7 months||27.25 in (69.2 cm)||26.5 in (67.3 cm)|
|8 months||27.75 in (70.6 cm)||27 in (68.7 cm)|
|9 months||28.25 in (72 cm)||27.5 in (70.1 cm)|
|10 months||28.75 in (73.3 cm)||28.25 in (71.5 cm)|
|11 months||29.25 in (74.5 cm)||28.75 in (72.8 cm)|
|12 months||29.75 in (75.7 cm)||29.25 in (74 cm)|
On average, babies grow 0.5 to 1 inch (1.5 to 2.5 cm) each month from birth to 6 months. From 6 to 12 months, babies grow an average of 3/8 inch (1 cm) per month.
Your doctor will measure and weigh your baby at routine checkups and mark their progress on a standard growth chart.
Your baby may grow more (growth spurts) or less during some periods. For example, infants tend to go through growth spurts at:
- 10 to 14 days
- 5 to 6 weeks
- 3 months
- 4 months
Your baby may be very fussy during a growth spurt and want to feed more. A growth spurt can last up to a week at a time.
Can you predict how tall your baby will be as an adult?
It’s difficult to predict how tall your baby will be later in life based on their length as a baby. Once your child is a bit older, you may be able to predict their adult height by doubling a boy’s height at age 2 or doubling a girl’s height at 18 months.
Premature babies are measured and weighed regularly, just as full-term babies are. But doctors may use an “adjusted age” to track the growth of premature babies over time.
For example, if your baby is 16 weeks old, but was born 4 weeks early, your pediatrician will subtract 4 weeks. Their adjusted age will be 12 weeks. Your baby should be meeting 12-week growth and
By age 2 or sooner, premature babies have usually caught up with their peers and your doctor won’t need to adjust their age any longer.
Your pediatrician will measure your baby for length at each appointment. This is an important measurement, but your doctor will likely be most concerned that your baby is gaining weight each month.
Infants should double their birth weight by age 5 months, and triple their birth weight by one year. Learn more about the average weight for male and female babies by month.
Remember, babies go through growth spurts. Your baby’s month-to-month progress on the growth chart isn’t as important as the trend of their curve overall.
If your child fails to grow or their growth has slowed during their first year, your doctor may refer you to a specialist. An endocrinologist may take blood tests, X-rays, or body or brain scans to determine why your baby has stopped growing.
In rare cases, your doctor may want to test your baby for:
Your doctor can recommend medications or hormone injections, if necessary.
Talk to your pediatrician if you’re concerned your child isn’t eating enough, meeting developmental milestones, or growing month to month.
Your baby’s diaper is a good indicator if they’re getting enough to eat. A newborn should have two to three wet diapers each day. After four to five days, babies should have five to six wet diapers each day. Stool frequency depends if your baby is breastfeeding or formula feeding.
Babies who are measuring in a healthy growth range at each checkup are likely getting enough to eat. Talk to your pediatrician if you’re concerned.
|Age||Feeding frequency||Amount of breastmilk or formula per feeding|
|Newborn||every 2 to 3 hours||1 to 2 ounces|
|2 weeks||every 2 to 3 hours||2 to 3 ounces|
|2 months||every 3 to 4 hours||4 to 5 ounces|
|4 months||every 3 to 4 hours||4 to 6 ounces|
|6 months||every 4 to 5 hours||up to 8 ounces|
Solid foods should be started between 6 to 8 months, though your doctor may recommend introducing solids earlier if your baby shows signs they’re ready. Once you introduce solids, continue to provide breastmilk or formula until your baby is at least 1 year of age.
Feeding frequency charts like the one above should be used as a guide only. It’s best to feed your baby when they’re hungry. Unless specifically advised by their pediatrician, avoid withholding food or forcing your baby to eat when they aren’t interested.
The average baby length per month is an important measurement. But it’s also important to make sure your baby is eating enough, gaining weight, and meeting certain
Talk to your pediatrician if you’re concerned. They can determine if your baby is growing as expected and if they’re a healthy length and weight for their age.