Baby Head Circumference Chart: Complete Guide to Measurement, Standards, and Concerns

Baby head circumference tracks brain growth and skull development from birth through early childhood. WHO head circumference-for-age charts help identify babies whose head size falls outside typical ranges or shows concerning growth patterns. Understanding how to measure head circumference accurately, interpret charts, and recognize red flags ensures proper monitoring of this critical development indicator.

Why Head Circumference Matters

Head circumference reflects brain growth and development. The skull grows to accommodate the rapidly developing brain, making head size a window into neurological health.

What head circumference indicates:

• Brain growth and development
• Cranial bone development
• Intracranial volume
• Potential neurological issues

Why we measure:

• Identify microcephaly (abnormally small head)
• Identify macrocephaly (abnormally large head)
• Detect hydrocephalus (excess fluid in brain)
• Monitor premature babies' brain development
• Track genetic conditions affecting head size

Head circumference is routinely measured at every well-child visit from birth through age 2-3, then less frequently afterward.

WHO Head Circumference-for-Age Standards

WHO developed head circumference standards as part of the Child Growth Standards Study (1997-2003).

Study basis:

• Healthy, well-nourished children
• Optimal environmental conditions
• Six countries (Brazil, Ghana, India, Norway, Oman, USA)
• Breastfed children

Age range: Birth to 60 months (most critical growth birth to 36 months)

Measurement: Circumference in centimeters or inches

Percentiles: 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th

Charts: Separate for boys and girls (boys have slightly larger heads on average)

Baby Head Circumference Chart: Boys

Baby Head Circumference Chart: Girls

Boys' heads average 0.3-0.5 inches larger than girls' at each age.

Expected Head Circumference Growth Patterns

Birth to 6 Months: Rapid Growth

Growth velocity: Approximately 0.5 inch (1.2 cm) per month

Total gain: 3-3.5 inches (7.5-9 cm) from birth to 6 months

Characteristics:

• Fastest head growth period of life
• Corresponds to rapid brain development
• Fontanelles (soft spots) still open
• Skull bones not yet fused

Normal variations:

• Molding from birth may temporarily affect shape and measurement
• Head shape rounds out in first weeks
• Growth spurts and plateaus normal

6 to 12 Months: Slowing Growth

Growth velocity: Approximately 0.25 inch (0.6 cm) per month

Total gain: 1.5-2 inches (4-5 cm) from 6 to 12 months

Characteristics:

• Growth velocity decreases compared to first 6 months
• Fontanelles begin closing (posterior fontanelle closes by 6 months)
• Skull bones beginning to fuse

12 to 24 Months: Continued Slowing

Growth velocity: Approximately 0.2 inch (0.5 cm) per month

Total gain: 2-2.5 inches (5-6 cm) from 12 to 24 months

Characteristics:

• Anterior fontanelle closes (typically 12-18 months)
• Skull bones continue fusing
• Growth rate continues declining

24 to 36 Months: Minimal Growth

Growth velocity: Approximately 0.15 inch (0.4 cm) per month

Total gain: 1.5-2 inches (4-5 cm) from 24 to 36 months

Characteristics:

• Very slow, steady growth
• Skull nearly fully formed
• Brain approaching 80% of adult size

By age 3, head circumference measurements become less critical as growth slows dramatically and skull is largely formed.

How to Measure Head Circumference Accurately

Accurate measurement requires proper technique and equipment.

Equipment Needed

Measuring tape:

• Soft, flexible fabric or paper tape
• Non-stretch material
• Centimeter markings (most charts use cm)
• Baby-safe (no sharp edges)

Not suitable:

• Rigid measuring tools
• Metal tapes
• Stretch tape measures

Measurement Technique

Step 1: Position the baby

• Baby can be sitting, lying, or held
• Head still (not moving)
• Calm and cooperative if possible

Step 2: Find correct placement

• Measure around largest part of head
• Front: Just above eyebrows (supraorbital ridge)
• Sides: Above ears
• Back: Most prominent part of back of head (occiput)

Step 3: Take measurement

• Wrap tape around head at points described
• Tape should be snug but not compressing
• Keep tape level (parallel to floor)
• Hair should be compressed under tape

Step 4: Read and record

• Read measurement where tape overlaps
• Record in centimeters (most precise)
• Note date and age

Step 5: Repeat for accuracy

• Measure 2-3 times
• Average the measurements
• If measurements vary by more than 0.5 cm, remeasure

Common Measurement Errors

Incorrect placement:

• Too high on forehead (misses supraorbital ridge)
• Too low (below eyebrows)
• Not over most prominent part of back of head

Tape not level:

• Tilted tape gives inaccurate measurement
• Check from front and side that tape is horizontal

Tape too loose:

• Doesn't capture true circumference
• Results in falsely large measurement

Hair not compressed:

• Thick hair adds 0.3-0.5 cm if not compressed
• Gently compress hair under tape

Baby moving:

• Movement makes accurate measurement impossible
• Wait for still moment or get help holding baby steady

Reading Head Circumference Charts

Step 1: Find Baby's Age

Locate age in months along horizontal axis of chart.

Step 2: Find Measurement

Locate head circumference in inches or centimeters along vertical axis.

Step 3: Plot Intersection

Find where age and measurement lines intersect on chart.

Step 4: Identify Percentile

See which percentile curve the point lands on or near (3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th).

Step 5: Track Over Time

Plot multiple measurements to see if baby tracks consistently along a curve or crosses percentile bands.

When Head Circumference Indicates Concerns

Microcephaly (Small Head)

Definition: Head circumference below 3rd percentile or more than 2 standard deviations below mean

Concerning patterns:

• Consistently below 2nd percentile
• Dropping 2+ percentile curves over time
• Not growing (flat growth curve)
• Head circumference growth significantly slower than weight and height

Possible causes:

• Genetic conditions
• Chromosomal abnormalities
• Congenital infections (TORCH infections)
• Exposure to toxins during pregnancy
• Severe malnutrition
• Craniosynostosis (premature skull fusion)

What it may indicate:

• Underdeveloped brain
• Neurological conditions
• Developmental delays

Action: Pediatrician referral to neurology for evaluation

Macrocephaly (Large Head)

Definition: Head circumference above 97th percentile or more than 2 standard deviations above mean

Concerning patterns:

• Consistently above 98th percentile
• Rapidly crossing percentile curves upward
• Head growing much faster than weight and height
• Accompanied by symptoms (vomiting, lethargy, developmental regression)

Possible causes:

• Familial (large head runs in family) - usually benign
• Hydrocephalus (fluid accumulation in brain)
• Brain tumors (rare)
• Genetic conditions (some forms of dwarfism)
• Subdural fluid collection

What it may indicate:

• Increased intracranial pressure (if hydrocephalus)
• Normal familial variation (if family history)
• Rarely: serious neurological conditions

Action: Pediatrician evaluation to distinguish benign from concerning causes

Crossing Percentile Curves

Concerning patterns:

• Crossing 2+ percentile curves in either direction over 3-6 months
• Rapid acceleration or deceleration of growth

Examples:

• Baby at 50th percentile at birth, dropping to 10th by 6 months
• Baby at 25th percentile at birth, jumping to 90th by 6 months

Why concerning: Sudden changes in growth trajectory can indicate developing problems even if current percentile seems normal

Disproportionate Growth

Concerning pattern: Head circumference percentile significantly different (3+ bands) from weight and height percentiles

Examples:

• Head at 95th percentile, weight and height at 25th
• Head at 10th percentile, weight and height at 75th

Why concerning: May indicate condition affecting brain growth independently from body growth

Familial Head Size Considerations

Head size has strong genetic component. Babies often have head sizes similar to their parents.

Familial macrocephaly:

• Large head runs in family
• Baby's head size proportional to parents' head sizes
• Growth follows consistent curve
• No symptoms or developmental concerns
• Usually benign

Familial microcephaly:

• Small head runs in family
• Baby's head size proportional to parents' head sizes
• Growth follows consistent curve
• Development normal
• Usually benign

When family history considered:

• Pediatrician may measure parents' head circumferences
• Compare baby's percentile to parental percentiles
• Familial patterns reduce concern if baby develops normally

Additional Assessments When Head Size Concerns Exist

Physical examination:

• Fontanelle assessment (bulging, sunken, size)
• Head shape evaluation
• Neurological examination

Developmental screening:

• Age-appropriate milestone achievement
• Cognitive, motor, language development

Imaging:

• Ultrasound (if fontanelle open)
• CT scan or MRI (if fontanelle closed or serious concern)
• Evaluate brain structure, fluid spaces, abnormalities

Genetic testing:

• If syndrome suspected
• Family history of genetic conditions
• Multiple congenital anomalies present

Repeat measurements:

• Close monitoring with frequent measurements
• Track growth velocity precisely
• Determine if pattern stabilizes or worsens

The Bottom Line on Baby Head Circumference Charts

Baby head circumference reflects brain growth and is routinely monitored from birth through age 2-3 using WHO growth standards. Expected growth is rapid in first 6 months (0.5 inch/month), slowing to 0.25 inch/month by 12 months and declining further thereafter.

Healthy head circumference shows consistent tracking along a percentile curve between the 3rd and 97th percentiles, with measurements proportional to weight and height percentiles. Concerning patterns include measurements consistently below 2nd or above 98th percentile, crossing 2+ percentile curves in either direction, or significant disproportion to body size.

Measure head circumference accurately by wrapping soft tape around the largest part of the head (above eyebrows, above ears, over most prominent part of back of head), keeping tape level and snug. Plot measurements on WHO charts and track trends over time.

When head size concerns arise, pediatricians evaluate family history (head size is genetic), developmental progress, and physical examination before determining whether imaging or specialist referral is needed. Most babies with large or small heads develop normally, especially when family patterns explain the measurements.

References

1. World Health Organization. WHO Child Growth Standards. Available at: https://www.who.int/tools/child-growth-standards
2. Centers for Disease Control and Prevention. Head Circumference Charts. Available at: https://www.cdc.gov/growthcharts/
3. American Academy of Pediatrics. Microcephaly and Macrocephaly Evaluation. Pediatrics. 2009.
4. Rollins JD, et al. Evaluation of Head Circumference in Children. American Family Physician. 2010.
5. Daymont C, et al. Head Circumference Distribution in a Large Primary Care Network. Pediatrics. 2012.