Head Circumference Percentile Calculator
Head Circumference Percentile
Calculate head circumference percentile based on age and sex (WHO standards, 0-5 years)
months
cm
Formula
Z-Score = (Measured HC - Median for age/sex) / Standard Deviation | Percentile derived from Z-Score using normal distribution | WHO Child Growth Standards (2006)
Frequently Asked Questions
What is a normal head circumference for a baby?
Normal head circumference varies by age and sex. At birth, average is about 34-35 cm for boys and 33-34 cm for girls. Head circumference between the 5th and 95th percentiles is generally considered normal. What matters most is consistent growth along a percentile curve.
What is microcephaly and macrocephaly?
Microcephaly is a head circumference below the 3rd percentile (or more than 2 standard deviations below the mean) for age and sex. Macrocephaly is above the 97th percentile. Both may warrant further evaluation, though some cases are familial and benign.
How often should head circumference be measured?
Head circumference is typically measured at every well-child visit during the first 2 years of life (at birth, 1, 2, 4, 6, 9, 12, 15, 18, and 24 months). After age 2, it is measured less frequently unless there are concerns.
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