GROWTH GUIDE · BIRTH TO 24 MONTHS

Baby head circumference percentile calculator

Head circumference is the measurement around a baby’s head. This reference compares that measurement with babies of the same age and sex in the WHO growth standard.

Calculate head circumference percentile ↗

Take a consistent measurement

Use a non-stretch tape around the widest part of the head, above the eyebrows and ears and around the back. A healthcare professional can confirm the technique and repeat a measurement that seems unexpected.

Understand the number

The 50th percentile is the middle of the reference distribution. A baby near the 25th percentile has a larger measurement than approximately 25% of the reference group at that age and sex. A percentile is not a percentage of ideal growth.

Head circumference is one part of an assessment. A calculator cannot interpret head shape, development, family history or the reason for a change.

Reference values by age

Newborn head circumference reference 1 month head circumference reference 2 month head circumference reference 3 month head circumference reference 4 month head circumference reference 6 month head circumference reference 8 month head circumference reference 9 month head circumference reference 12 month head circumference reference 15 month head circumference reference 18 month head circumference reference 24 month head circumference reference

Reference, not diagnosis

Talk to your healthcare professional about a measurement or trend that concerns you. This tool does not correct age for babies born prematurely.

Source: WHO head circumference-for-age tables. Read the calculation methodology.

Review status: Maintained by Baby Growth and technically reviewed on 29 September 2026. Calculations and product ranges are checked against the cited WHO, CDC and manufacturer sources. This independent tool has not received clinical review and does not replace professional care.