Boys Head chart for babies 8 month old baby

Head circumference chart for 8-Month-Old boys

Head size and development for baby boys at 8-Month-Old.

Head circumference percentiles for 8-Month-Old boys

CDC growth chart data shows the following head circumference distribution for baby boys at 8-Month-Old:

• 5th percentile: 42.4 cm (16.7 in)

• 25th percentile: 43.7 cm (17.2 in)

• 50th percentile (median): 44.6 cm (17.6 in)

• 75th percentile: 45.5 cm (17.9 in)

• 95th percentile: 46.7 cm (18.4 in)

A percentile ranking tells you where your child's measurement falls among baby boys of the same age. The 50th percentile is the statistical midpoint of the population.

Head circumference and development for baby boys

By eight months, the rapid early gains in head circumference have settled into a steadier pace. Brain development continues intensely, but the explosive early phase of head growth has passed.

Recording measurements over time

Continue recording head measurements at every health check and plotting them on the percentile chart. A sudden change in the rate of head circumference growth - either faster or slower than expected - warrants review. Trust your instincts: you are with your baby every day and are well placed to notice changes that a periodic check-up might not immediately capture.

Developmental milestones alongside head growth

As your baby becomes more mobile - sitting, crawling, pulling to stand - they naturally vary their head position throughout the day, which supports balanced skull shape. Ongoing brain development at this age is reflected in rapidly increasing social engagement, babbling, and purposeful hand use. If head circumference measurement concerns arise at a check-up, a paediatrician can assess the full developmental picture.

Frequently asked questions

What is a normal head circumference for this age?

The percentile table on this page shows the full range of typical head circumferences. All values from the 5th to the 95th percentile are within normal limits. As with all growth measurements, the pattern of growth over time is more informative than any single reading - a baby growing consistently at the 15th percentile is growing normally.

How fast does head circumference grow in the first year?

Head circumference grows approximately 10-12 cm in the first year of life - roughly 2 cm per month in the first 3 months, slowing to about 1 cm per month from 3-6 months, and 0.5 cm per month from 6-12 months. By 12 months, the average head circumference has grown from approximately 34-35 cm at birth to around 46-47 cm.

What is the fontanelle and when does it close?

The fontanelle is the soft spot on the top of a baby's head where the skull bones have not yet fused. There are two fontanelles: the larger anterior (front) fontanelle, which typically closes between 9 and 18 months, and the smaller posterior (back) fontanelle, which usually closes by 2-3 months. Both allow the skull to expand rapidly as the brain grows during the first years of life.

Data sources and methodology

The percentile ranges on this page are drawn from CDC growth chart data from the National Center for Health Statistics and WHO Child Growth Standards (for children under 5). CDC data published May 30, 2000, with 2022 extended BMI tables. Percentiles are modelled using the LMS method (Box-Cox transformation), which accounts for the skewed distribution of measurements at each age. All measurements are given in metric units with imperial equivalents.

Growth charts are screening tools, not diagnostic ones. If you have concerns about your child's measurements, a GP or paediatrician is the right first step.