Baby head circumference (head size) chart by month

This chart shows the WHO head circumference-for-age percentiles for baby girls and boys from birth to 24 months, in cm with in for the median. Use the calculator below to find your baby’s head circumference percentile for their exact age.

Sex

Units

Date of birth Date measured Weight (kg) Length (cm) Head circumference (cm)

Chart

Enter a date of birth and at least one measurement to see the percentile.

Key numbers

At birth, the WHO median head circumference is 33.9 cm (13.3 in) for girls and 34.5 cm (13.6 in) for boys.
At 6 months, the median is 42.2 cm (16.6 in) for girls and 43.3 cm (17.1 in) for boys.
At 12 months, the median is 44.9 cm (17.7 in) for girls and 46.1 cm (18.1 in) for boys.
At 24 months, the median is 47.2 cm (18.6 in) for girls and 48.3 cm (19.0 in) for boys.
In the first year, median head circumference grows by about 11.0 cm for girls and 11.6 cm for boys, and 76% of that first-year growth happens in the first 6 months.

Girls: average head circumference and percentiles by month (WHO)

Values in cm at each percentile. The median is the average head circumference for that age; it is also shown in in.

Age	3th	15th	Median	85th	97th	Median (in)
Birth	31.7	32.7	33.9	35.1	36.1	13.3
1 month	34.3	35.3	36.5	37.8	38.8	14.4
2 months	36.0	37.0	38.3	39.5	40.5	15.1
3 months	37.2	38.3	39.5	40.8	41.8	15.6
4 months	38.2	39.3	40.6	41.9	42.9	16.0
5 months	39.1	40.2	41.5	42.8	43.8	16.3
6 months	39.8	40.9	42.2	43.5	44.6	16.6
7 months	40.4	41.5	42.8	44.2	45.3	16.9
8 months	40.9	42.0	43.4	44.7	45.8	17.1
9 months	41.4	42.5	43.8	45.2	46.3	17.3
10 months	41.8	42.9	44.2	45.6	46.7	17.4
11 months	42.1	43.2	44.6	46.0	47.1	17.6
12 months	42.4	43.5	44.9	46.3	47.4	17.7
13 months	42.6	43.8	45.2	46.6	47.7	17.8
14 months	42.9	44.0	45.4	46.8	48.0	17.9
15 months	43.1	44.2	45.7	47.1	48.2	18.0
16 months	43.3	44.4	45.9	47.3	48.4	18.1
17 months	43.5	44.6	46.1	47.5	48.6	18.1
18 months	43.6	44.8	46.2	47.7	48.8	18.2
19 months	43.8	45.0	46.4	47.9	49.0	18.3
20 months	44.0	45.1	46.6	48.0	49.2	18.3
21 months	44.1	45.3	46.7	48.2	49.4	18.4
22 months	44.2	45.4	46.9	48.4	49.5	18.5
23 months	44.4	45.6	47.0	48.5	49.7	18.5
24 months	44.5	45.7	47.2	48.7	49.9	18.6

Boys: average head circumference and percentiles by month (WHO)

Values in cm at each percentile. The median is the average head circumference for that age; it is also shown in in.

Age	3th	15th	Median	85th	97th	Median (in)
Birth	32.1	33.1	34.5	35.8	36.9	13.6
1 month	35.1	36.1	37.3	38.5	39.5	14.7
2 months	36.9	37.9	39.1	40.3	41.3	15.4
3 months	38.3	39.3	40.5	41.7	42.7	16.0
4 months	39.4	40.4	41.6	42.9	43.9	16.4
5 months	40.3	41.3	42.6	43.8	44.8	16.8
6 months	41.0	42.1	43.3	44.6	45.6	17.1
7 months	41.7	42.7	44.0	45.3	46.3	17.3
8 months	42.2	43.2	44.5	45.8	46.9	17.5
9 months	42.6	43.7	45.0	46.3	47.4	17.7
10 months	43.0	44.1	45.4	46.7	47.8	17.9
11 months	43.4	44.4	45.8	47.1	48.2	18.0
12 months	43.6	44.7	46.1	47.4	48.5	18.1
13 months	43.9	45.0	46.3	47.7	48.8	18.2
14 months	44.1	45.2	46.6	47.9	49.0	18.3
15 months	44.3	45.4	46.8	48.2	49.3	18.4
16 months	44.5	45.6	47.0	48.4	49.5	18.5
17 months	44.7	45.8	47.2	48.6	49.7	18.6
18 months	44.9	46.0	47.4	48.8	49.9	18.7
19 months	45.0	46.2	47.5	48.9	50.0	18.7
20 months	45.2	46.3	47.7	49.1	50.2	18.8
21 months	45.3	46.4	47.8	49.2	50.4	18.8
22 months	45.4	46.6	48.0	49.4	50.5	18.9
23 months	45.6	46.7	48.1	49.5	50.7	18.9
24 months	45.7	46.8	48.3	49.7	50.8	19.0

How to read this chart

A percentile tells you how a measurement compares with other children of the same age and sex. At the 50th percentile (the median), half of children measure more and half measure less. At the 15th percentile, 15 out of 100 children measure less.

Anything between the 3rd and the 97th percentile is within the usual range on the WHO chart. Pediatricians pay more attention to the direction of the curve over several visits than to any single number: a baby who stays near the 15th percentile is usually growing just as steadily as one who stays near the 85th.

Percentiles here come from the official WHO LMS tables, calculated at each whole month. Between months, the calculator interpolates for your baby’s exact age.

Common questions

What are normal head circumference values by age?

On the WHO standard, the 3rd to 97th percentile runs from 31.7–36.1 cm for newborn girls and 32.1–36.9 cm for newborn boys; at 4 months 38.2–42.9 cm (girls) and 39.4–43.9 cm (boys); at 6 months 39.8–44.6 cm and 41.0–45.6 cm; at 12 months 42.4–47.4 cm and 43.6–48.5 cm.

How do you measure head circumference?

Wrap a flexible, non-stretch tape around the widest part of the head: just above the eyebrows and ears and around the most prominent part of the back of the head. Take the largest of a few readings.

How do I find my baby’s head size percentile?

Head size on a growth chart means head circumference. Measure around the widest part of the head, then enter it with your baby’s date of birth in the calculator on this page to get the WHO percentile. For reference, the WHO median is 33.9 cm (13.3 in) for newborn girls and 34.5 cm (13.6 in) for newborn boys, and 44.9 cm (17.7 in) and 46.1 cm (18.1 in) at 12 months.

Why do doctors measure head circumference?

Head size reflects brain growth, which is fastest in the first year. Pediatricians look at the trend over several visits, especially a curve that crosses percentile lines, more than at a single number.

Should I use the WHO or the CDC growth chart?

The CDC recommends the WHO growth charts for children under 2 years in the United States, and the CDC charts from age 2. The WHO charts describe how healthy breastfed babies grow in good conditions; the CDC charts describe a reference group of US children.

Follow your baby’s curve over time

Growthling plots every checkup on the WHO or CDC chart and shows the percentile for each one. Free to sign up.

Start tracking free