Child Growth Chart Calculator: Height, Weight and BMI Percentiles

How to use it

1. Choose Girl or Boy. The WHO charts are different for each.
2. Enter the date of birth and the date you measured (today is filled in). If you only know the age, switch to Years + months. The date of birth is more exact, especially for babies, who change week by week.
3. Type the weight in kg or lb and the height (or length for babies) in cm or feet and inches. You can enter just one of them.
4. For children under 5, say whether you measured lying down or standing. WHO measures length lying down until 2 years and height standing after that; the tool applies WHO’s 0.7 cm correction if you did it the other way.
5. Read the percentile for each measure, the plain-English sentence and the WHO category, then look at the chart. Tap the chart buttons to switch between height, weight, BMI and weight-for-length.

What a percentile means

A percentile compares your child with healthy children of the same age and sex. If height is on the 62nd percentile, your child is taller than about 62 of 100 children of that age and shorter than about 38. The 50th percentile is the middle (the median), not a target: a child on the 10th or the 90th percentile can be just as healthy. Children come in different sizes, mostly because their parents do.

Doctors often use the z-score (SD score) instead, which the tool also shows. A z-score of 0 is the median, −1 and +1 are roughly the 16th and 84th percentiles, and −2 and +2 are roughly the 2nd and 98th. The WHO categories below are set on z-scores.

Under 5, the tool uses the WHO Child Growth Standards, which describe how healthy breastfed children grow when their needs are met. They were built from children in Brazil, Ghana, India, Norway, Oman and the USA. From 5 to 19 years it uses the WHO Growth Reference 2007. Both come from the official WHO tables, and the percentile is worked out with the WHO’s LMS method.

WHO categories: weight-for-length/height and BMI, under 5

WHO categories: BMI-for-age, 5 to 19 years

WHO categories: height and weight for age

Between these lines the result is shown as normal or in the usual range. Weight-for-age is not used after 10 years, because in puberty it cannot tell height from body fat; BMI-for-age is used instead.

Why one reading does not tell the whole story

A single dot on a chart is a snapshot. A wriggly baby, a full nappy, shoes left on or a different scale can easily move the result by several percentiles. Children also grow in bursts, and a cold or tummy bug can pause weight gain for a week or two.

What doctors look at is the line that several measurements make over months. A healthy line usually runs roughly alongside the curves, even if it is low or high. A line that rises or falls steeply, crosses curves, or goes flat is worth a check, as the WHO training course on child growth assessment explains. So measure the same way each time, write down the date, and bring your notes to check-ups.

How to measure correctly at home

• Weight: use the same scale each time, on a hard floor, with your child in light clothes and no shoes or nappy. For a baby who will not lie still, weigh yourself, then weigh yourself holding the baby and take the difference (this is less exact).
• Length (under 2): two people. Lay your baby on their back on a firm surface with the head touching a wall or board. Gently straighten the knees, keep the feet flat upwards, and mark where the heels are. Measure from the board to the mark.
• Height (2 and over): no shoes, heels together against a wall, with heels, bottom and shoulders touching it. Ask your child to look straight ahead, rest a flat book on the top of the head at a right angle to the wall, mark, and measure to the nearest millimetre.
• Same time of day: children are a little taller in the morning and weight changes after meals, so measure at a similar time each time.
• Units: check kg versus lb and cm versus inches. A mix-up is the most common reason for a strange result.

Growth charts in India: WHO and IAP

The Indian Academy of Pediatrics (IAP) recommends the WHO Child Growth Standards for children under 5, which is what this tool uses. For 5 to 18 years, IAP published its own growth charts for height, weight and BMI in 2015, based on Indian children from 14 cities, and uses BMI cut-offs equal to an adult BMI of 23 (overweight) and 27 (obesity). Your paediatrician may plot your child on these IAP charts, so a percentile from them can differ a little from the WHO result here. The charts are on the IAP website.

Sources

• WHO Child Growth Standards (birth to 5 years): official expanded LMS and percentile tables for weight-for-age, length/height-for-age, weight-for-length, weight-for-height and BMI-for-age.
• WHO Multicentre Growth Reference Study Group (2006). WHO child growth standards: methods and development. Geneva: WHO.
• WHO Growth Reference 2007 (5 to 19 years): height-for-age, BMI-for-age and weight-for-age (5 to 10 years) tables.
• de Onis M et al. Development of a WHO growth reference for school-aged children and adolescents. Bull World Health Organ 2007;85:660–7.
• WHO (2008). Training course on child growth assessment. Measuring and interpreting growth.
• Khadilkar V et al. Revised IAP growth charts for height, weight and BMI for 5- to 18-year-old Indian children. Indian Pediatr 2015;52:47–55.
• Indian Academy of Pediatrics: IAP growth charts.

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