If you have ever wondered, “What is the average circumference of baby’s head?”, you are not alone. Head circumference is one of the routine measurements taken during a baby’s health checkups, along with weight and length. It helps pediatricians monitor how your baby is growing over time.
A baby’s head size naturally varies from one child to another. There is no single “perfect” head circumference for every newborn or infant. Instead, doctors consider a baby’s age, sex, gestational age, measurement accuracy and, most importantly, how the measurement changes over time.
The average baby head circumference is generally around the mid-30-centimeter range at birth, but boys and girls have slightly different WHO reference values. For example, the WHO median head circumference at birth is about 34.5 cm for boys and 33.9 cm for girls.
This guide explains normal baby head circumference, provides a baby head circumference chart by age, explains head circumference percentiles and shows you how to measure your baby’s head correctly at home.
Quick answer: There is no single normal head circumference for all babies. WHO growth standards provide age- and sex-specific reference values, and pediatricians look at the baby’s growth pattern over time rather than one measurement alone.
What Is the Average Circumference of Baby’s Head?
The average circumference of a baby’s head changes rapidly during infancy because a baby’s head grows quickly during the first year of life.
According to WHO Child Growth Standards, the median head circumference at birth is approximately:
- Boys: 34.5 cm
- Girls: 33.9 cm
By 6 months, the median is approximately:
- Boys: 43.3 cm
- Girls: 42.2 cm
At 12 months:
- Boys: 46.1 cm
- Girls: 44.9 cm
These are median values, not minimum or maximum limits. Many healthy babies will have a head circumference above or below these numbers. WHO provides separate head circumference-for-age charts and percentile tables for boys and girls from birth through 5 years.
This is why the average newborn head circumference should not be used as a pass-or-fail number. Your pediatrician will usually plot your baby’s measurement on an appropriate growth chart and monitor the pattern at subsequent visits.
Average Newborn Head Circumference
The average newborn head circumference is around 34 cm, although the exact reference value differs by sex.
WHO’s median at birth is 34.5 cm for boys and 33.9 cm for girls. The WHO percentile tables also show a wider distribution around these median values, demonstrating that newborn head size naturally varies.
Birth head circumference can also be influenced by factors such as gestational age, birth size and the circumstances surrounding delivery. For premature babies, healthcare professionals may use growth references appropriate for gestational age rather than simply comparing the baby with a full-term newborn.
How Baby Head Circumference Changes With Age
A baby’s head grows particularly quickly during infancy. The rate of growth gradually slows as the child gets older.
WHO has specific standards for head circumference by age, including both percentile and z-score charts. The standards allow healthcare professionals to compare a child’s measurement with children of the same age and sex.
The important point is that a baby’s head circumference should be considered as part of the overall growth picture.
Average vs. Normal Head Circumference
The terms average baby head circumference and normal baby head circumference do not mean exactly the same thing.
The average or median represents the midpoint of a reference population. A normal measurement can occur above or below that midpoint.
For example, if your baby’s head circumference is below the median, that does not automatically mean there is a problem. Likewise, a measurement above the median does not automatically indicate an abnormality.
Baby Head Circumference Chart by Age
The following table uses WHO Child Growth Standards and shows selected reference values for baby head circumference by age. The median represents the 50th percentile, while the 3rd and 97th percentiles demonstrate the broader range shown in the WHO simplified percentile tables.
| Baby Age | Boys: 3rd–97th Percentile | Boys: Median | Girls: 3rd–97th Percentile | Girls: Median |
|---|---|---|---|---|
| Birth | 32.1–36.9 cm | 34.5 cm | 31.7–36.1 cm | 33.9 cm |
| 1 month | 35.1–39.5 cm | 37.3 cm | 34.3–38.8 cm | 36.5 cm |
| 2 months | 36.9–41.3 cm | 39.1 cm | 36.0–40.5 cm | 38.3 cm |
| 3 months | 38.3–42.7 cm | 40.5 cm | 37.2–41.9 cm | 39.5 cm |
| 4 months | 39.4–43.9 cm | 41.6 cm | 38.2–43.0 cm | 40.6 cm |
| 5 months | 40.3–44.8 cm | 42.6 cm | 39.0–43.9 cm | 41.5 cm |
| 6 months | 41.0–45.6 cm | 43.3 cm | 39.7–44.6 cm | 42.2 cm |
| 7 months | 41.7–46.3 cm | 44.0 cm | 40.4–45.3 cm | 42.8 cm |
| 8 months | 42.2–46.9 cm | 44.5 cm | 40.9–45.9 cm | 43.4 cm |
| 9 months | 42.6–47.4 cm | 45.0 cm | 41.3–46.3 cm | 43.8 cm |
| 10 months | 43.0–47.8 cm | 45.4 cm | 41.7–46.8 cm | 44.2 cm |
| 11 months | 43.4–48.2 cm | 45.8 cm | 42.0–47.1 cm | 44.6 cm |
| 12 months | 43.6–48.5 cm | 46.1 cm | 42.3–47.5 cm | 44.9 cm |
| 18 months | 44.9–49.9 cm | 47.4 cm | 43.6–48.8 cm | 46.2 cm |
| 24 months | 45.7–50.8 cm | 48.3 cm | 44.6–49.8 cm | 47.2 cm |
*Source: WHO Child Growth Standards, head circumference-for-age percentiles. Values are reference measurements and should not be used to diagnose a health condition. *
The table is useful when you are looking for a baby head circumference chart, but remember that a percentile is not a grade. A baby does not need to be at the 50th percentile to be healthy.
Baby Head Circumference by Month
Parents often search for baby head circumference by age or a specific monthly measurement. Here’s how to understand the numbers.
Head Circumference at Birth
At birth, the WHO median is approximately 34.5 cm for boys and 33.9 cm for girls. The reference range is broader than the median, so individual newborns can have different head sizes and still be healthy.
If your baby was born prematurely, ask your pediatrician how the measurement should be interpreted because gestational age can be important.
1-Month-Old Baby Head Circumference
The median 1-month-old baby head circumference is about 37.3 cm for boys and 36.5 cm for girls according to WHO standards.
Your baby’s measurement may be higher or lower than this value. What matters is how it compares with the appropriate growth chart and how it changes at future visits.
2-Month-Old Baby Head Circumference
At 2 months, the WHO median is about 39.1 cm for boys and 38.3 cm for girls.
Parents should avoid comparing their baby’s measurement with another 2-month-old because individual growth patterns can differ considerably.
3-Month-Old Baby Head Circumference
The median 3-month-old baby head circumference is approximately 40.5 cm for boys and 39.5 cm for girls.
If you are searching for the normal head circumference for a 3-month-old baby, remember that the median is only one point on the growth chart.
4-Month-Old Baby Head Circumference
At 4 months, the WHO median is approximately 41.6 cm for boys and 40.6 cm for girls.
Head growth is still relatively rapid during this period, although the rate gradually slows.
5-Month-Old Baby Head Circumference
At 5 months, the median is around 42.6 cm for boys and 41.5 cm for girls.
A measurement slightly above or below the average does not automatically indicate a concern.
6-Month-Old Baby Head Circumference
The average head circumference of a 6-month-old baby is approximately 43.3 cm for boys and 42.2 cm for girls at the WHO median.
If you are wondering about the normal head circumference for a 6-month-old baby, use the age- and sex-specific percentile rather than comparing your baby’s number with a single average.
7-Month-Old Baby Head Circumference
At 7 months, the WHO median is approximately 44.0 cm for boys and 42.8 cm for girls.
8-Month-Old Baby Head Circumference
At 8 months, the median is around 44.5 cm for boys and 43.4 cm for girls.
9-Month-Old Baby Head Circumference
At 9 months, the WHO median is approximately 45.0 cm for boys and 43.8 cm for girls.
Parents looking for a normal head circumference for a 9-month-old baby should consider the complete percentile chart rather than focusing only on the median.
10-Month-Old Baby Head Circumference
At 10 months, the median head circumference is approximately 45.4 cm for boys and 44.2 cm for girls.
11-Month-Old Baby Head Circumference
At 11 months, the WHO median is around 45.8 cm for boys and 44.6 cm for girls.
12-Month-Old Baby Head Circumference
At 12 months, the median is approximately 46.1 cm for boys and 44.9 cm for girls.
So, if you are wondering what the normal head circumference for a 1-year-old baby is, there is a range of expected measurements rather than one fixed number.
18-Month-Old Baby Head Circumference
By 18 months, the WHO median is approximately 47.4 cm for boys and 46.2 cm for girls.
2-Year-Old Head Circumference
At 24 months, the WHO median is approximately 48.3 cm for boys and 47.2 cm for girls.
Growth charts continue to be useful for understanding the overall pattern. In clinical settings, WHO standards are recommended for children from birth to 2 years in the United States, after which CDC growth charts are generally used.
Baby Head Circumference Chart for Boys vs. Girls
Boys and girls have separate head circumference growth charts because their growth patterns are not identical.
In general, the WHO median head circumference is slightly larger for boys than girls at the same age. For example, at birth the median is 34.5 cm for boys compared with 33.9 cm for girls. At 12 months, it is 46.1 cm for boys compared with 44.9 cm for girls.
This is why you should use the appropriate infant head circumference chart for your baby’s sex.
When assessing baby head size, healthcare professionals may also consider weight, length, gestational age and other aspects of development.
What Is a Normal Head Circumference for a Baby?
There is no single measurement that defines a normal head circumference for babies.
Instead, pediatricians generally consider:
- Baby’s age
- Sex
- Gestational age
- Measurement accuracy
- Head circumference percentile
- Previous measurements
- Overall growth pattern
- Other health and developmental information
A baby at the 15th percentile can be healthy, just as a baby at the 85th percentile can be healthy.
The key is not to assume that the 50th percentile is the “ideal” head size. Percentiles describe how a measurement compares with a reference population; they do not grade a child’s health.
What Does Baby Head Circumference Percentile Mean?
A baby head circumference percentile tells you how your baby’s measurement compares with measurements of children of the same age and sex in the reference population.
For example, a baby around the 50th percentile has a head circumference near the median of the reference population.
What Is the 50th Percentile?
The 50th percentile is the median.
It does not mean “perfect,” “best” or “healthiest.” It simply means that approximately half of the reference population has a measurement below it and half above it.
What Does a Low Head Circumference Percentile Mean?
A low percentile means the baby’s head circumference is smaller than that of many children of the same age and sex in the reference population.
However, a low percentile does not automatically mean there is a health problem.
Family characteristics, gestational age, measurement differences and an individual child’s growth pattern all matter.
What Does a High Head Circumference Percentile Mean?
Similarly, a high percentile means the measurement is larger than that of many children in the reference population.
A high percentile is not automatically a sign of a medical problem. A pediatrician may look at previous measurements and other clinical information before deciding whether further evaluation is needed.
Why Percentile Changes Matter
The trend over time can be more informative than one isolated measurement.
If a baby’s head circumference has consistently followed a particular growth pattern, that information can help the pediatrician understand the child’s growth.
Conversely, an unexpected change in growth trajectory may warrant closer assessment.
The CDC emphasizes that growth charts are tools that contribute to an overall picture of a child’s health and are not intended to be used as the sole diagnostic instrument.
How to Measure a Baby’s Head Circumference Correctly
Knowing how to measure baby’s head circumference correctly is important because even a small measurement error can affect the percentile.
What You Need
Use a flexible, narrow, non-stretchable measuring tape.
A soft measuring tape used for sewing can work if it does not stretch.
How to Measure Baby Head Circumference at Home
Follow these steps:
- Remove anything that could interfere with the measurement, such as a hat or bulky hair accessory.
- Place the tape across the forehead just above the eyebrows and the supraorbital ridges.
- Wrap the tape around the widest part of the back of the head, around the occiput.
- Keep the tape level on both sides.
- Move the tape slightly up or down to locate the maximum circumference.
- Make sure the tape is snug enough to compress the hair without pressing excessively against the skull.
- Record the measurement in centimeters.
- Ideally, repeat the measurement to make sure you get a consistent result.
The American Academy of Pediatrics recommends a narrow, non-stretchable tape and advises measuring the maximum head circumference and recording it to the nearest 0.1 cm.
If your home measurement differs from one taken at your pediatrician’s office, do not immediately assume that your baby’s head has changed. Differences in positioning and technique can affect the result.
Common Mistakes When Measuring a Baby’s Head
When measuring baby head circumference at home, parents should avoid:
- Measuring over a hat
- Using a stretchy tape
- Holding the tape too loosely
- Pulling the tape excessively tight
- Measuring at a different position each time
- Comparing measurements taken with different techniques
- Relying on a single home measurement to determine whether a baby is healthy
For accurate growth tracking, consistency matters.
How Often Is a Baby’s Head Circumference Measured?
Healthcare professionals routinely measure head circumference during infancy because it provides useful information about growth.
The American Academy of Pediatrics recommends measuring head circumference at visits through the 2-year visit. The AAP describes head circumference as a proxy measure for brain growth and recommends accurate measurement using an appropriate technique.
You do not necessarily need to measure your baby’s head every day or every week at home. Frequent measurements can actually create unnecessary anxiety because normal measurement variation can occur.
Instead, keep your baby’s routine pediatric appointments and discuss any concerns with your healthcare provider.
What Factors Can Affect a Baby’s Head Circumference?
Several factors can influence baby head size, including:
Genetics
Parents and close family members naturally have different head sizes. A baby’s head circumference can reflect family characteristics.
Sex
WHO growth standards provide separate charts for boys and girls because their typical growth patterns differ.
Gestational Age
A premature baby may have a different expected growth pattern than a full-term newborn. Healthcare professionals take gestational age into account when interpreting growth.
Birth Size
Overall size at birth can also be relevant when assessing growth.
Measurement Technique
Incorrect tape placement or inconsistent measurement can make the head circumference appear larger or smaller than it actually is.
Individual Growth Pattern
Every child grows differently. A measurement should therefore be interpreted alongside previous measurements and other growth parameters.
Small Head vs. Large Head in Babies: When Should Parents Be Concerned?
It is natural for parents to become concerned when their baby’s head appears smaller or larger than expected.
However, head circumference should not be interpreted in isolation.
When a Baby’s Head Seems Smaller Than Expected
If your baby’s measurement appears smaller than the average baby head circumference, remember that being below the median does not automatically indicate a problem.
A pediatrician may consider:
- The baby’s growth history
- Head circumference percentile
- Gestational age
- Family head size
- Weight and length
- Development
- Other physical findings
If the measurement is consistently unusual or the growth pattern changes unexpectedly, discuss it with your pediatrician.
When a Baby’s Head Seems Larger Than Expected
A larger-than-average head circumference does not automatically mean something is wrong either.
Some babies naturally have larger heads, including babies whose parents or family members also have larger head sizes.
The important question is whether the measurement follows an expected growth pattern and whether there are other findings that concern the healthcare professional.
When to Speak With Your Pediatrician
Talk with your pediatrician if:
- You are consistently concerned about your baby’s head circumference.
- Measurements appear substantially different between visits.
- Your baby’s growth pattern changes unexpectedly.
- Your pediatrician has raised a concern about head growth.
- You have concerns about your baby’s overall growth or development.
Do not attempt to diagnose a condition using an online baby head circumference chart alone.
Head Circumference, Weight and Length: Why All Three Matter
A baby’s growth is more than just head size. Pediatricians generally consider multiple measurements together.
| Measurement | What It Helps Monitor |
|---|---|
| Head circumference | Head and brain growth |
| Weight | Body weight gain and overall growth |
| Length | Linear growth |
The American Academy of Pediatrics describes anthropometric measurements as part of the overall assessment of infant and child growth and nutritional status.
This means a baby’s infant head size should be considered alongside weight, length and the child’s broader health picture.
If you are tracking your baby’s growth at home, consider keeping a record of all three measurements rather than focusing only on head circumference.
WHO vs. CDC Growth Charts for Baby Head Circumference
Parents may come across both WHO and CDC growth charts when researching an infant head circumference chart.
The WHO Child Growth Standards include head circumference-for-age charts and tables for boys and girls from birth through 5 years.
For children from birth to 2 years, the CDC recommends using WHO Child Growth Standards in U.S. clinical settings. At age 2 years, CDC recommends transitioning to CDC Growth Charts.
The WHO standards are intended to describe healthy growth under favorable conditions and can be applied internationally. WHO states that its 0–5-year growth standards can be applied to children regardless of ethnicity, socioeconomic status or feeding method.
For this article, the baby head circumference chart above uses WHO Child Growth Standards so parents have a clearly identified reference source.
Frequently Asked Questions About Baby Head Circumference
What is the average circumference of a newborn baby’s head?
The WHO median newborn head circumference is approximately 34.5 cm for boys and 33.9 cm for girls. However, healthy newborns can have measurements above or below the median.
What is a normal baby head circumference?
There is no single normal baby head circumference. The expected measurement depends on age, sex and other factors. Pediatricians use age- and sex-specific growth charts to interpret the measurement.
What is the normal head circumference for a newborn?
The WHO median is approximately 34.5 cm for boys and 33.9 cm for girls at birth. A baby’s individual measurement may be higher or lower than this value.
What is the normal head circumference for a 3-month-old baby?
The WHO median is approximately 40.5 cm for boys and 39.5 cm for girls at 3 months. The full percentile range should be considered rather than the median alone.
What is the normal head circumference for a 6-month-old baby?
At 6 months, the WHO median is approximately 43.3 cm for boys and 42.2 cm for girls.
What is the normal head circumference for a 1-year-old baby?
At 12 months, the WHO median head circumference is approximately 46.1 cm for boys and 44.9 cm for girls.
Does head circumference indicate brain growth?
Head circumference is used as a proxy measure for brain growth during infancy. It is one part of a broader growth assessment and should not be interpreted by itself.
How do I measure my baby’s head circumference at home?
Use a narrow, non-stretchable tape around the widest part of the baby’s head. Position it just above the eyebrows and around the back of the head at the occiput. Keep the tape level and record the measurement accurately.
What percentile should my baby’s head circumference be?
There is no single percentile that every baby should be at. Healthy babies can fall at different points on the growth chart. Your pediatrician will consider the percentile and the growth pattern over time.
Is a small head circumference always a concern?
No. A measurement below the median does not automatically mean there is a problem. Family characteristics, gestational age, measurement accuracy and the child’s overall growth pattern are important.
Is a large head circumference always a concern?
No. Some healthy babies naturally have larger head sizes. A pediatrician may evaluate the measurement in the context of previous measurements, family characteristics and the child’s overall health.
Do boys and girls have different head circumference charts?
Yes. WHO provides separate baby head circumference charts for boys and girls because their growth patterns differ.
How fast does a baby’s head grow?
Head growth is fastest during early infancy and gradually slows as a baby gets older. WHO provides head circumference velocity standards that describe expected changes over specific age intervals.
Should I worry if my baby’s head circumference percentile changes?
A change in percentile does not automatically mean something is wrong. However, an unexpected or persistent change in growth pattern should be discussed with your pediatrician, who can interpret it alongside other growth measurements and clinical information.
Medical Disclaimer
This article is intended for general educational purposes and should not replace advice from your baby’s pediatrician or other qualified healthcare professional.
Growth charts are tools used to help monitor growth and should not be used on their own to diagnose a medical condition. The CDC specifically notes that growth charts contribute to an overall assessment of a child’s health rather than serving as a standalone diagnostic tool.
If you are concerned about your baby’s head circumference, growth, development or any other aspect of their health, speak with your pediatrician.
Growth chart source: World Health Organization (WHO) Child Growth Standards – Head Circumference-for-Age.
Measurement guidance: American Academy of Pediatrics (AAP) – Anthropometric Measurements.
Growth chart guidance: Centers for Disease Control and Prevention (CDC) – WHO Growth Standards for children from birth to 2 years.
