Child growth and development percentile calculator
This English page translates the Korean child growth guide and keeps the same WHO 2024 and Korean Pediatric Society 2024 reference logic. It estimates height, weight, head circumference, BMI, percentile, Z-score, and growth velocity from the source pure functions.
What the calculator measures
The Korean source explains that a child should not be judged by a single average value. The calculator compares the same sex and age group, then reports percentile and Z-score for height, weight, BMI, and head circumference. WHO 2024 curves are used up to 60 months, and the Korean Pediatric Society 2024 revised curves are used for older children.
Percentile means where the child sits among 100 same-sex children of the same age. The 50th percentile is the middle of the reference group, the 3rd percentile marks the lower extreme, and the 97th percentile marks the upper extreme. The Z-score expresses the same idea as standard deviations from the median.
- 97th percentile or higher: much larger than peers, review overweight or obesity risk when the metric is weight or BMI.
- 75th to 97th percentile: above average, usually interpreted with growth trend.
- 25th to 75th percentile: middle 50 percent reference band.
- 3rd to 25th percentile: below average, trend monitoring is recommended.
- Below the 3rd percentile: growth delay or medical review may be needed.
BMI and velocity interpretation
Child BMI must be interpreted by percentile, not by the adult BMI labels alone. The Korean guide uses the pediatric bands: below the 5th percentile for underweight, 5th to 85th for normal weight, 85th to 95th for overweight, and 95th percentile or higher for obesity.
Growth velocity is the change over time. A child can be small but healthy if the percentile curve is stable. A sharp fall across percentile lines is more concerning than a single low measurement, which is why the Korean page saves recent measurement records and compares monthly height and weight change.
- Infancy, 0 to 1 year: about 25 cm per year in height and 6 to 7 kg per year in weight.
- Toddler period, 1 to 3 years: about 10 to 12 cm per year and 2 to 3 kg per year.
- Preschool, 3 to 6 years: about 6 to 8 cm per year and about 2 kg per year.
- School age, 6 to 12 years: about 5 to 6 cm per year and 2 to 3 kg per year.
- Puberty: about 8 to 12 cm per year during the growth spurt.
Example scenarios from the Korean guide
A 6-month boy with height 67.5 cm, weight 8.2 kg, and head circumference 43.5 cm is shown as near the middle of the reference curves. The example reports height around the 50th percentile, weight around the 60th percentile, head circumference around the 55th percentile, and BMI 18.0 around the 70th percentile.
A 3-year girl with height 94.0 cm and weight 12.5 kg is used to show why nutrition and trend review matter. The example has height around the 40th percentile but weight around the 10th percentile, so the issue is not height alone but a low-weight pattern that may need dietary review.
A 9-year boy with height 135.0 cm and weight 42.0 kg shows the opposite risk. Height is around the 60th percentile, but weight and BMI can approach the 97th and 96th percentiles. The Korean guide recommends lifestyle review and pediatric consultation when the pattern persists.
Healthy growth checklist
The guide emphasizes nutrition, sleep, activity, and regular measurement. Growing children generally need protein, calcium, vitamin D, iron, and zinc. Sleep is important because growth hormone is secreted mainly during deep sleep, and consistent sleep timing matters as much as total hours.
Recommended home measurement intervals are every 3 to 6 months for height and weight. Korean infant health checkups are scheduled at 4, 9, 18, 30, 42, 54, and 66 months, and school health checkups occur in key grades. If height does not increase for more than 6 months or a child crosses percentiles quickly, professional review is safer than self-diagnosis.