🧠Baby Head Circumference Percentile (2026)
Head circumference is measured around the widest part of your baby's head — just above the eyebrows and ears — and is one of the three core growth measurements at every well-baby visit. It reflects healthy brain growth during the first two years, when the brain grows faster than at any other time. In the first 3 months, head circumference increases about 2 cm/month; 3-6 months about 1 cm/month; 6-12 months about 0.5 cm/month.
How to read it
As with weight and length, the trend matters most. A head that consistently tracks the same percentile is reassuring. A head crossing several percentile lines up or down, or a fontanelle that bulges or sinks, warrants a call to your pediatrician. Most of the time, it is simply your baby's natural growth pattern. Head circumference is measured with a non-stretchable tape at the largest occipitofrontal circumference.
Why head circumference matters
Head circumference is a direct window into brain growth. In the first two years, your baby's brain triples in size — from about 350g at birth to over 1000g by age 2. This is why pediatricians measure the head at every visit: a head that grows too slowly may signal a problem with brain development, while one that grows too rapidly can indicate excess fluid (hydrocephalus). The overwhelming majority of babies have perfectly normal head growth that simply follows their genetic curve. The measurement itself takes seconds — a quick loop of a tape measure — but the information it provides across visits is invaluable.
Average head circumference by age (reference, 50th percentile)
| Age | Boys (50th) | Girls (50th) |
|---|---|---|
| Newborn (0 months) | 13.6 in · 34.5 cm | 13.3 in · 33.9 cm |
| 6 months | 17.2 in · 43.8 cm | 16.8 in · 42.7 cm |
| 12 months | 18.4 in · 46.7 cm | 17.9 in · 45.5 cm |
| 18 months | 19.0 in · 48.2 cm | 18.5 in · 47.0 cm |
| 24 months | 19.4 in · 49.3 cm | 18.9 in · 48.1 cm |
Head circumference shown in cm and inches. Your pediatrician uses calibrated tools; home measurements are approximations for general understanding only. The WHO head circumference charts are used worldwide for ages 0-24 months. See full month-by-month tables on each age page.
Frequently asked questions
What is baby head circumference?
Head circumference is measured around the widest part of your baby's head — just above the eyebrows and ears — and is one of the three core growth measurements at every well-baby visit. It reflects healthy brain growth during the first two years, when the brain grows faster than at any other time. In the first 3 months, head circumference increases about 2 cm/month; 3-6 months about 1 cm/month; 6-12 months about 0.5 cm/month.
How is head circumference measured?
Head circumference is measured with a non-stretchable tape around the widest part of the head — just above the eyebrows and ears, around the occipitofrontal circumference. Your pediatrician uses calibrated tools for accuracy. Home measurements are approximations only.
What is the average head size for a baby?
At birth, the median head circumference is about 34.5 cm (13.6 in) for boys and 33.9 cm (13.3 in) for girls. By 12 months, it reaches about 46.7 cm (18.4 in) for boys and 45.5 cm (17.9 in) for girls. These are WHO reference averages — your pediatrician tracks the trend, which matters most.
When should I worry about my baby's head size?
A head that consistently tracks the same percentile is reassuring. Concern arises when head circumference crosses several percentile lines up or down, or if the fontanelle (soft spot) bulges or sinks. Head growth that is too fast or too slow can both warrant investigation — but most of the time, the curve is simply your baby's natural pattern.
How fast does a baby's head grow?
Head circumference grows about 2 cm/month in the first 3 months, 1 cm/month from 3-6 months, and 0.5 cm/month from 6-12 months. After 12 months, growth slows to about 0.25 cm/month. This rapid early growth reflects the astonishing pace of brain development in the first year.
What is the soft spot (fontanelle) and when does it close?
The anterior fontanelle (the larger soft spot on top) typically closes between 12-18 months. The posterior fontanelle (smaller, at the back) usually closes by 2-3 months. A bulging fontanelle can indicate increased pressure; a sunken one can signal dehydration. Both warrant an immediate call to your pediatrician.
Does head size predict intelligence?
No. Head circumference within the normal range has no correlation with intelligence. What matters is steady growth along the curve, not the absolute size. Many brilliant people have heads at every percentile. This is an educational reference only.
Can I measure my baby's head at home?
You can, but home measurements are less accurate than your pediatrician's. Use a flexible, non-stretchable tape and measure at the widest point. Use the number as a general reference only — your pediatrician's measurement at well-baby visits is the one that counts for tracking the growth curve.