Head Circumference Percentile Calculator
Calculate head circumference percentile for infants and young children — a key indicator of brain growth.
What is Head Circumference Percentile?
Head circumference (HC) is a sensitive indicator of brain development in the first 2–3 years of life. Most healthy babies follow a consistent percentile through the first year. Crossing two channels up or down warrants paediatric evaluation, as may microcephaly (under 3rd percentile) or macrocephaly (above 97th percentile). HC tracking continues until age 3 in most countries.
How is it calculated?
Tape is placed across the most prominent point at the back of the head and just above the eyebrows, parallel to the floor. The percentile is computed using age- and sex-specific reference means and SDs approximated from the WHO 0–5 year head circumference standards.
Frequently Asked Questions
- How is head circumference measured?
- With a non-stretch tape across the largest occipito-frontal circumference.
- Is microcephaly always serious?
- No — small heads can be familial. Concern rises when paired with developmental delays.
- How often is HC measured?
- At every well-baby visit through age 2; less often after.
- What does macrocephaly mean?
- Possible benign familial macrocephaly or, rarely, hydrocephalus — paediatric review is needed.