Your baby's head circumference is one of the first measurements healthcare providers will take of your newborn.
Doctors call it a fronto-occipital circumference (or OFC), and it's a good indication of your baby's brain development. Taking the measurement is an important part of well-baby health care, because the growth of your baby's head shows the development of their central nervous system.
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Numbers outside normal ranges – or a dramatic shift in your baby's trending numbers over time – can alert your baby's doctor to any possible problems.
What is average newborn head circumference?
The average newborn's head circumference is about 13.47 inches (34.2 cm). At 1 month old, it's about 14.53 inches (36.9 cm). Boys' heads (and bodies) are slightly larger, but the difference is less than half an inch (1 cm).
What's a normal baby head circumference?
There's no one number to define a normal baby head circumference at a given age, but there are charts that provide ranges. These charts give the average head circumference for a boy or girl at a given age, and they allow your baby's doctor to compare your baby's head size with the average – as well as with your baby's growth over time. The normal range is usually defined as approximately between the 5th and 95th percentiles.
So if your baby's head circumference is in the 50th percentile, that means that they have the average head circumference. If their number falls in the 30th percentile on the chart, it means that 30 percent of babies the same age have a smaller head circumference, and 70 percent have a larger head circumference.
Doctors often chart preterm babies using a preterm curve.
Learn more about how growth charts work.
When will my baby's head circumference be measured?
The first time your baby's head will be measured is shortly after birth. The medical staff will take the measurement promptly because the charts used for comparison were developed measuring babies before 24 hours of age.
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At birth, your baby's head is 25 percent of its future adult size, and by age 3, the brain is 80 percent of its adult size. Because birth to 3 years old is a period of rapid brain growth, your child's healthcare provider will measure their head circumference at every well-baby and well-child visit up to 2 years. (Head circumference is also measured in older children with abnormal growth.)
The doctor will enter this number on your baby's growth chart, along with their length and weight. Each time a measurement is taken, your baby's provider will compare the measurement with your baby's past measurements and with the normal ranges for your child's sex and age.
You can measure your baby's head circumference at home, too, if you want. But it's not necessary (your baby's doctor will routinely measure and chart the numbers for you), and it's hard to do it accurately.
When should I be concerned about my baby's head circumference?
If your baby's head circumference is outside the normal range for their age and sex, their healthcare provider will want to check for problems.
If your baby's head circumference is much smaller than average, it may be a sign that their brain has stopped growing or isn't growing properly. This might be due to an infection or a genetic condition. Your baby's doctor will probably refer you to a pediatric neurologist or neurosurgeon if your baby has microcephaly (the name for a very small head size).
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If your baby's head circumference is much larger than average, it may be a sign of hydrocephalus, which is a buildup of fluid in and around the brain. This rare condition can increase the pressure in your baby's head. Other causes of a large head size are brain tumors or genetic conditions. Again, you'll be referred to a pediatric neurologist or neurosurgeon who can diagnose and treat the condition.
Baby head circumference chart
These are the numbers your baby's healthcare provider will use to compare your baby's head circumference to average ranges. Doctors use charts developed by the World Health Organization (WHO) for babies from birth to 24 months. For ages 2 to 3 years, doctors use charts developed by the Centers for Disease Control and Prevention (CDC).
Note that the transition from WHO numbers to CDC numbers isn't perfectly seamless at 2 years (because WHO and the CDC use different standards), but they're close enough for doctors to continue to chart them effectively.
Girls: Head circumference from birth to 24 months
Girls in weeks
| Age (weeks) | Head circumference |
|---|
| 0 | 33.9 cm | 13.35 inches |
| 1 | 34.6 | 13.62 |
| 2 | 35.2 | 13.86 |
| 3 | 35.8 | 14.10 |
| 4 | 36.4 | 14.33 |
| 5 | 36.8 | 14.49 |
| 6 | 37.3 | 14.69 |
| 7 | 37.7 | 14.84 |
| 8 | 38.0 | 14.96 |
| 9 | 38.4 | 15.12 |
| 10 | 38.7 | 15.24 |
| 11 | 39.0 | 15.35 |
| 12 | 39.3 | 15.47 |
| 13 | 39.5 | 15.55 |
Girls in months
| Age (months) | Head circumference |
|---|
| 0 | 33.9 cm | 13.35 inches |
| 1 | 36.5 | 14.37 |
| 2 | 38.3 | 15.08 |
| 3 | 39.5 | 15.55 |
| 4 | 40.6 | 15.98 |
| 5 | 41.5 | 16.34 |
| 6 | 42.2 | 16.61 |
| 7 | 42.8 | 16.85 |
| 8 | 43.4 | 17.09 |
| 9 | 43.8 | 17.24 |
| 10 | 44.2 | 17.40 |
| 11 | 44.6 | 17.56 |
| 12 | 44.9 | 17.68 |
| 13 | 45.2 | 17.80 |
| 14 | 45.4 | 17.87 |
| 15 | 45.7 | 17.99 |
| 16 | 45.9 | 18.07 |
| 17 | 46.1 | 18.15 |
| 18 | 46.2 | 18.19 |
| 19 | 46.4 | 18.27 |
| 20 | 46.6 | 18.35 |
| 21 | 46.7 | 18.39 |
| 22 | 46.9 | 18.46 |
| 23 | 47.0 | 18.50 |
| 24 | 47.2 | 18.58 |
Boys: Head circumference from birth to 24 months
Boys in weeks
| Age (weeks) | Average head circumference |
|---|
| 0 | 34.5 cm | 13.58 inches |
| 1 | 35.2 | 13.86 |
| 2 | 35.9 | 14.13 |
| 3 | 36.5 | 14.37 |
| 4 | 37.1 | 14.61 |
| 5 | 37.6 | 14.80 |
| 6 | 38.1 | 15.00 |
| 7 | 38.5 | 15.16 |
| 8 | 38.9 | 15.32 |
| 9 | 39.2 | 15.43 |
| 10 | 39.6 | 15.59 |
| 11 | 39.9 | 15.71 |
| 12 | 40.2 | 15.83 |
| 13 | 40.5 | 15.95 |
Boys in months
| Age (months) | Head circumference |
|---|
| 0 | 34.5 cm | 13.58 inches |
| 1 | 37.3 | 14.69 |
| 2 | 39.1 | 15.39 |
| 3 | 40.5 | 15.95 |
| 4 | 41.6 | 16.38 |
| 5 | 42.6 | 16.77 |
| 6 | 43.3 | 17.05 |
| 7 | 44.0 | 17.32 |
| 8 | 44.5 | 17.52 |
| 9 | 45.0 | 17.72 |
| 10 | 45.4 | 17.87 |
| 11 | 45.8 | 18.03 |
| 12 | 46.1 | 18.15 |
| 13 | 46.3 | 18.23 |
| 14 | 46.6 | 18.35 |
| 15 | 46.8 | 18.43 |
| 16 | 47.0 | 18.50 |
| 17 | 47.2 | 18.58 |
| 18 | 47.4 | 18.66 |
| 19 | 47.5 | 18.70 |
| 20 | 47.7 | 18.78 |
| 21 | 47.8 | 18.82 |
| 22 | 48.0 | 18.90 |
| 23 | 48.1 | 18.94 |
| 24 | 48.3 | 19.02 |
Girls: Head circumference from 2 to 3 years
| Age (months) | Average head circumference |
|---|
| 23.5 | 47.41 cm | 18.67 inches |
| 24.5 | 47.54 | 18.72 |
| 25.5 | 47.66 | 18.76 |
| 26.5 | 47.78 | 18.81 |
| 27.5 | 47.89 | 18.85 |
| 28.5 | 48.00 | 18.90 |
| 29.5 | 48.10 | 18.94 |
| 30.5 | 48.19 | 18.97 |
| 31.5 | 48.28 | 19.01 |
| 32.5 | 48.37 | 19.04 |
| 33.5 | 48.45 | 19.08 |
| 34.5 | 48.52 | 19.10 |
| 35.5 | 48.60 | 19.13 |
| 36 | 48.63 | 19.15 |
Boys: Head circumference from 2 to 3 years
| Age (months) | Average head circumference |
|---|
| 23.5 | 48.60 cm | 19.13 inches |
| 24.5 | 48.72 | 19.18 |
| 25.5 | 48.83 | 19.22 |
| 26.5 | 48.94 | 19.27 |
| 27.5 | 49.04 | 19.31 |
| 28.5 | 49.13 | 19.34 |
| 29.5 | 49.22 | 19.38 |
| 30.5 | 49.31 | 19.41 |
| 31.5 | 49.38 | 19.44 |
| 32.5 | 49.46 | 19.47 |
| 33.5 | 49.53 | 19.50 |
| 34.5 | 49.59 | 19.52 |
| 35.5 | 49.65 | 19.55 |
| 36 | 49.68 | 19.56 |
Your baby's healthcare provider will chart your baby's height and weight too. Use our baby height and weight tracker to keep tabs yourself.
Understanding your baby's growth and development is more than charting numbers, of course. Check out our articles on baby development to learn more about your baby's growth, month by month.
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