Length percentiles for a 1-month-old boy

For a 1-month-old boy, the WHO median length (50th percentile) is 54.7 cm. Most healthy boys this age measure between 51.1 cm and 58.4 cm, the 3rd and 97th percentiles.

Percentile table

Percentile	Value	Imperial
3rd	51.1 cm	20.1 in
5th	51.5 cm	20.3 in
15th	52.7 cm	20.8 in
25th	53.4 cm	21.0 in
50th (median)	54.7 cm	21.5 in
75th	56.0 cm	22.1 in
85th	56.7 cm	22.3 in
95th	57.9 cm	22.8 in
97th	58.4 cm	23.0 in

Values from the WHO table, rounded to one decimal.

Source: WHO Child Growth Standards, length-for-age table. Every value on this page is checked automatically against the published WHO table before publishing, and the calculator uses WHO's LMS method. Updated October 2, 2026. Corrections and questions: ahozon@benbasha.com

Percentile calculator

Enter your child's measurement to see the WHO percentile. It uses the same WHO 2006 engine as the Ahozon app, and nothing you type leaves this page.

How growth looks at this age

From birth to 1 month, the median rises by 4.8 cm. The gap between the 3rd and 97th percentile is 7.3 cm at this age, compared with 7.1 cm at birth, because the curves fan out as children grow. For comparison, the median for girls of the same age is 53.7 cm. Relative to their size, the gap between the girls' and boys' medians is larger now than at birth.

Length grows fastest in the first months of life.

WHO curves, birth to 5 years. Lines show the 3rd, 15th, 50th, 85th and 97th percentiles. The dot marks 1 month.

What does the percentile mean?

A percentile compares a child with healthy children of the same age and sex from the WHO Multicentre Growth Reference Study. At the 40th percentile, 40 out of 100 children are shorter and 60 are longer. Anything between the 3rd and 97th percentile is in the normal range. What matters most is that a child keeps following a similar curve over time.

How to measure

Under two years, length is measured lying down on a measuring board, with the legs gently straightened.

When to ask your pediatrician

Talk to your pediatrician or child health nurse if a measurement is below the 3rd or above the 97th percentile, or if your child's percentile changes a lot between visits, for example crossing two of the main percentile lines. A single measurement says little; the trend over time matters most.

General information, not medical advice. One measurement says little on its own: talk to your pediatrician or child health nurse about your child's growth.