head circumference percentiles P3–P97, Japan

Japan’s published head circumference figures, P3 to P97 month by month, up to 5 years. Boys and girls separately.

This table spans two standards: r5-nyuyoji-2023 from 0 months, then who-cgs-2006 for older ages. The numbers step at the join — that is the reference changing, not the child.

boy

Age in years runs along the bottom and head circumference（cm） up the side. The five lines are, from the bottom, the 3rd, 15th, 50th, 85th and 97th percentiles, ranging from 31.1 to 53.5. The full figures are in the table above.

Japan percentile curves for head circumference, boy.

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yearsmonths

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Japan · head circumference, boy（cm）
Age	P3	P15	P50	P85	P97
0 months	31.1	32.3	33.7	35.0	36.1
1 months	34.4	35.6	36.8	38.1	39.0
2 months	36.4	37.5	38.8	40.1	41.1
3 months	37.9	39.0	40.3	41.6	42.6
4 months	39.0	40.1	41.5	42.8	43.8
5 months	40.0	41.1	42.4	43.7	44.8
6 months	40.7	41.8	43.2	44.5	45.6
7 months	41.4	42.5	43.8	45.2	46.3
8 months	42.0	43.1	44.4	45.8	46.9
9 months	42.5	43.6	44.9	46.3	47.4
10 months	42.9	44.0	45.3	46.7	47.9
11 months	43.2	44.3	45.7	47.1	48.3
12 months	43.5	44.6	46.0	47.4	48.6
13 months	43.8	44.9	46.3	47.7	48.9
14 months	44.1	45.2	46.5	48.0	49.2
15 months	44.4	45.4	46.8	48.2	49.4
16 months	44.5	45.6	47.0	48.4	49.6
17 months	44.7	45.8	47.2	48.6	49.8
18 months	44.9	46.0	47.4	48.8	50.0
19 months	45.1	46.2	47.6	49.0	50.2
20 months	45.3	46.4	47.8	49.2	50.4
21 months	45.5	46.6	47.9	49.4	50.6
22 months	45.6	46.7	48.1	49.5	50.8
23 months	45.8	46.8	48.2	49.7	50.9
2 years	45.9	47.0	48.4	49.8	51.1
2y 3m	46.3	47.4	48.8	50.3	51.5
2y 6m	46.7	47.8	49.1	50.6	51.9
2y 9m	47.0	48.1	49.5	51.0	52.3
3 years	46.8	48.0	49.5	50.9	52.1
3y 3m	47.0	48.2	49.7	51.2	52.4
3y 6m	47.2	48.4	49.9	51.4	52.6
3y 9m	47.3	48.5	50.1	51.6	52.8
4 years	47.5	48.7	50.2	51.7	53.0
4y 3m	47.6	48.8	50.4	51.9	53.1
4y 6m	47.7	49.0	50.5	52.0	53.3
4y 9m	47.8	49.1	50.6	52.2	53.4
5 years	47.9	49.2	50.7	52.3	53.5

girl

Age in years runs along the bottom and head circumference（cm） up the side. The five lines are, from the bottom, the 3rd, 15th, 50th, 85th and 97th percentiles, ranging from 30.8 to 52.6. The full figures are in the table above.

Japan percentile curves for head circumference, girl.

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yearsmonths

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Japan · head circumference, girl（cm）
Age	P3	P15	P50	P85	P97
0 months	30.8	32.0	33.3	34.6	35.5
1 months	33.9	34.9	36.1	37.3	38.2
2 months	35.7	36.8	38.0	39.2	40.1
3 months	37.0	38.1	39.4	40.6	41.6
4 months	38.0	39.1	40.4	41.7	42.6
5 months	38.9	40.0	41.3	42.6	43.6
6 months	39.6	40.8	42.1	43.4	44.4
7 months	40.3	41.5	42.8	44.1	45.1
8 months	40.9	42.1	43.4	44.7	45.8
9 months	41.4	42.6	43.9	45.3	46.3
10 months	41.8	42.9	44.3	45.7	46.7
11 months	42.1	43.3	44.7	46.0	47.0
12 months	42.3	43.5	44.9	46.3	47.3
13 months	42.6	43.8	45.2	46.5	47.6
14 months	42.8	44.0	45.4	46.8	47.8
15 months	43.0	44.2	45.7	47.0	48.1
16 months	43.2	44.5	45.9	47.2	48.3
17 months	43.4	44.7	46.1	47.4	48.5
18 months	43.7	44.9	46.3	47.7	48.7
19 months	43.9	45.1	46.5	47.9	48.9
20 months	44.1	45.3	46.7	48.1	49.2
21 months	44.3	45.5	46.9	48.3	49.4
22 months	44.4	45.7	47.1	48.5	49.6
23 months	44.6	45.8	47.3	48.6	49.7
2 years	44.8	46.0	47.4	48.8	49.9
2y 3m	45.2	46.5	47.9	49.3	50.4
2y 6m	45.6	46.8	48.3	49.7	50.8
2y 9m	46.0	47.2	48.7	50.1	51.2
3 years	45.9	47.0	48.5	50.0	51.2
3y 3m	46.1	47.3	48.7	50.2	51.4
3y 6m	46.3	47.5	49.0	50.4	51.6
3y 9m	46.5	47.7	49.2	50.6	51.8
4 years	46.7	47.9	49.3	50.8	52.0
4y 3m	46.8	48.0	49.5	51.0	52.2
4y 6m	47.0	48.2	49.6	51.1	52.3
4y 9m	47.1	48.3	49.8	51.3	52.5
5 years	47.2	48.4	49.9	51.4	52.6

About this table

The figures come from the government survey itself — the 2023 Infant and Toddler Growth Survey published through e-Stat — rather than from the paediatric endocrine society’s charts, which are drawn from the 2000 survey.
The survey covers birth to 6 years, and head circumference only to 3. Japan publishes school-age figures separately, but as means without a percentile distribution, so nothing above 6 years can be read from them. WHO covers that range here instead.