A child’s head circumference is an important measurement that helps parents and healthcare providers monitor healthy growth during infancy and early childhood. It is also useful when choosing hats, helmets, or other headwear that should fit comfortably without being too tight or too loose.
While age-based head size charts provide a helpful reference, every child develops at their own pace. Genetics, nutrition, and overall growth all influence head circumference. This guide includes average head size charts for boys and girls from birth to 3 years, along with practical tips for measuring head circumference accurately.
Girls: Head circumference from birth to 24 months
Girls in weeks
During the first two years, a girl’s head grows rapidly, especially during the first 12 months. The following charts show average head circumference measurements.
| Age (months) | Head circumference(cm) | Head circumference(inches) |
| 0 | 33.9 | 13.35 |
| 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(cm) | Head circumference(inches) |
| 0 | 33.9 | 13.35 |
| 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
Boys generally have slightly larger average head circumferences than girls throughout infancy. These measurements are intended as a growth reference rather than a strict standard.
| Age (months) | Head circumference(cm) | Head circumference(inches) |
| 0 | 34.5 | 13.58 |
| 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(cm) | Head circumference(inches) |
| 0 | 34.5 | 13.58 |
| 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
Between ages two and three, head growth slows considerably compared to infancy. Even so, regular measurements can still help monitor healthy development.
| Age (months) | Head circumference(cm) | Head circumference(inches) |
| 23.5 | 47.41 | 18.67 |
| 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) | Head circumference(cm) | Head circumference(inches) |
| 23.5 | 48.60 | 19.13 |
| 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 |
Understanding Head Growth During Early Childhood
Head circumference increases rapidly during the first year of life because the brain develops quickly during this period. Growth gradually slows throughout the second and third years, although steady increases remain normal.
It’s important to remember that these charts represent average measurements, not strict targets. Many healthy children naturally fall slightly above or below the averages.
Pediatricians typically evaluate head circumference alongside height, weight, and developmental milestones to gain a complete picture of a child’s overall growth.
Why Measure Head Size?
Measuring head circumference is about more than choosing the right hat or helmet. It is one of the key measurements pediatricians use to monitor healthy brain and skull development during infancy and early childhood.
Head size measurements can help:
- Track healthy growth over time.
- Identify changes in growth patterns.
- Select properly fitting hats, helmets, and protective headgear.
- Improve comfort and safety during everyday activities.
- Ensure sports helmets provide adequate protection.
While a single measurement offers useful information, doctors typically evaluate head circumference alongside height, weight, and developmental milestones to get a complete picture of a child’s growth.
How to Measure Head Size
Taking an accurate measurement only requires a flexible measuring tape and a few simple steps.
Step 1: Use a Flexible Measuring Tape
A soft tailor’s measuring tape provides the most accurate results. Avoid using rulers or rigid tape measures.
Step 2: Position the Tape Correctly
Wrap the tape around the largest part of the head, making sure it passes:
- Just above the eyebrows
- Above both ears
- Around the most prominent part at the back of the head
The tape should remain level all the way around.
Step 3: Keep the Tape Snug
The tape should fit comfortably against the skin without compressing the hair or pressing into the scalp.
Step 4: Record the Measurement
Measure in centimeters whenever possible, as most pediatric growth charts use metric units. You can also record the equivalent measurement in inches for shopping purposes.
For the most consistent results, repeat the measurement once or twice and use the average if necessary.
Head Size Variations and Considerations
Head circumference varies naturally from one child to another. Several factors influence these differences.
Genetics
Children often inherit head size characteristics from their parents and close relatives. A larger or smaller head circumference may simply reflect family traits.
Growth Rate
Every child grows at a different pace. Some experience rapid growth during infancy, while others grow more gradually.
Nutrition
Proper nutrition supports healthy overall growth, including brain and skull development during the early years.
Premature Birth
Babies born prematurely may follow different growth patterns during the first months of life. Pediatricians often use adjusted age when evaluating growth.
Because of these natural variations, head circumference should always be interpreted within the broader context of a child’s overall health rather than as an isolated measurement.
Using Head Size Charts in Practice
Head size charts are invaluable for practical applications such as selecting appropriately sized hats, helmets, and headgear. They also aid in monitoring growth and development in infants and children.
Balancing factors like accuracy and ease of use poses challenges in applying head size charts effectively. This ensures optimal fit and supports healthy development across various age groups, emphasizing the significance of informed decision-making in utilizing head size charts.
Using Head Size Charts for Hats and Helmets
Head circumference charts are especially useful when purchasing protective headgear or everyday accessories.
Choosing the Right Hat Size
A properly fitted hat should:
- Sit comfortably above the eyebrows.
- Stay in place without slipping.
- Feel snug without leaving pressure marks.
- Allow room for natural movement.
Many children’s hat manufacturers list recommended head circumference ranges, making it easy to compare measurements before purchasing.
Choosing the Right Helmet Size
Helmets require a more precise fit because they are designed to provide protection.
A properly fitted helmet should:
- Sit level on the head.
- Cover the forehead adequately.
- Remain stable without excessive movement.
- Fasten securely under the chin.
Always follow the helmet manufacturer’s sizing guide rather than relying solely on age recommendations.
When Should You Be Concerned About Head Size?
Image Prompt: Pediatrician reviewing a child’s growth chart with parents during a routine checkup in a modern medical office.
Most children naturally fall within a healthy range of head sizes. However, if your child’s head circumference changes dramatically over a short period or falls well outside the expected growth pattern, consult your pediatrician.
Medical professionals evaluate:
- Previous head measurements
- Height and weight growth
- Family history
- Developmental milestones
- Overall health
Avoid drawing conclusions based on a single measurement. Regular checkups provide a much clearer understanding of your child’s growth.
Conclusion
A head size chart is a valuable tool for tracking healthy growth and selecting properly fitting hats, helmets, and other headwear. While age-based averages provide helpful guidance, every child develops at their own pace, so individual measurements are always the best reference.
By measuring head circumference correctly and comparing it with reliable size charts, parents can make more informed decisions about both health monitoring and everyday purchases. Combined with regular pediatric checkups, these charts help ensure children stay comfortable, protected, and supported throughout their early years.
FAQs
Why is head circumference measured during pediatric checkups?
Head circumference is one of the standard growth measurements used to monitor brain and skull development during infancy and early childhood. Tracking measurements over time helps healthcare providers assess whether a child is growing as expected.
How often should I measure my child’s head?
Parents generally don’t need to measure head circumference frequently at home unless advised by a healthcare professional. During infancy, pediatricians typically record head circumference at routine wellness visits.
What if my child’s head measurement is above or below the average?
Not every healthy child matches the average values shown in a head size chart. Genetics, growth patterns, and individual development all influence head circumference. If you have concerns, discuss them with your child’s pediatrician rather than relying on a single measurement.
Can I use head circumference to buy hats online?
Yes. Measuring your child’s head and comparing the result with the manufacturer’s sizing chart is the most reliable way to choose a comfortable hat size.
How do I know if a helmet fits correctly?
A properly fitted helmet should sit level on the head, cover the forehead, and remain secure without excessive movement. Always adjust the straps according to the manufacturer’s instructions before use.
At what age does head growth slow down?
Head growth is fastest during the first year of life. It gradually slows during the second and third years, although steady growth continues throughout early childhood.