liminfoChild Growth Calculator
Free web tool: Child Growth Calculator
Weight Percentile
32.8%ile
Height Percentile
25.2%ile
BMI Percentile
79.2%ile
BMI: 17.2 - Normal
About Child Growth Calculator
The Baby Growth Calculator uses the World Health Organization (WHO) 2006 Child Growth Standards to evaluate infant development from birth to 12 months of age. Parents, pediatric nurses, and healthcare providers can enter the baby's age in months (0–12), biological sex, current weight in kilograms, and length in centimeters to instantly receive weight-for-age percentile, height-for-age percentile, BMI-for-age percentile, and a weight status classification (Underweight, Normal, Overweight, or Obese).
The tool applies a Z-score algorithm derived from the WHO reference data, which provides separate growth curves for male and female infants. For each measurement, the mean and standard deviation for the child's specific age group are retrieved from built-in WHO reference tables, a Z-score is computed as (observed − mean) / SD, and that Z-score is converted to a percentile using a numerical approximation of the cumulative normal distribution. BMI is calculated as weight (kg) divided by height (m) squared and then similarly assessed against age- and sex-specific norms.
Growth monitoring in the first year of life is clinically important because rapid developmental changes occur during this period. A child consistently below the 5th percentile for weight or height may warrant further evaluation for feeding difficulties, metabolic issues, or growth disorders. Conversely, a BMI percentile above the 85th percentile signals overweight and above the 95th percentile signals obesity according to standard pediatric guidelines. This tool gives parents a quick reference between clinical visits to track trends over time.
Key Features
- WHO 2006 Child Growth Standards reference data for boys and girls separately
- Weight-for-age percentile with Z-score calculation using sex- and age-specific mean and SD
- Height-for-age percentile computed from WHO length/height-for-age reference tables
- BMI calculation (kg/m²) with age-adjusted percentile and classification
- Four-category weight status output: Underweight (<5th), Normal (5th–85th), Overweight (85th–95th), Obese (>95th)
- Supports age range 0 to 12 months with separate male and female growth curves
- Real-time recalculation — results update immediately when any input changes
- 100% client-side processing — infant health data never leaves your browser
Frequently Asked Questions
What growth standard does this calculator use?
The calculator uses the WHO Multicentre Growth Reference Study (MGRS) 2006 standards, which are based on children from six countries raised under optimal conditions (breastfed, non-smoking environments). These are the international reference standard for children from birth to 5 years, used by pediatricians worldwide.
What does a weight percentile of 25 mean?
A weight percentile of 25 means the baby weighs more than 25% of babies of the same age and sex according to WHO standards, and less than 75%. Percentiles between the 5th and 85th are generally considered within the normal range. Single measurements are less meaningful than trends over multiple visits.
My baby is at the 3rd height percentile. Should I be worried?
A percentile below the 5th for height (classified as Underweight in height terms) may warrant discussion with a pediatrician, especially if the trend is downward across visits, if the child was born at a higher percentile, or if other growth parameters are also low. This tool is for reference only and does not replace clinical evaluation.
Why does the calculator only cover 0–12 months?
The tool uses reference tables with monthly data points covering the first 12 months, which represents the period of most rapid postnatal growth. The WHO standards extend to 5 years, but those age groups require different data tables and z-score algorithms that are not included in this version.
How is BMI interpreted differently in infants than in adults?
Adult BMI thresholds (e.g., 25 for overweight, 30 for obese) do not apply to infants. In children, BMI is evaluated as a percentile relative to age and sex norms. A BMI at the 85th percentile or above is considered overweight, and above the 95th percentile is obese, per standard pediatric classification systems.
Does the calculator account for prematurity?
No. The calculator uses chronological age (months since birth) without correcting for gestational age. For premature infants, many pediatricians use corrected age (subtracting weeks of prematurity from chronological age) when plotting on growth charts. You should manually calculate the corrected age in months before entering it into this tool.
Are the results the same as what a pediatrician would calculate?
The tool uses the same WHO reference data and Z-score to percentile conversion method. However, clinical growth assessment involves additional factors such as birth weight, parental height, feeding history, and examination findings. Always consult a healthcare provider for clinical decisions.
Is my child's health data stored or transmitted?
No. All calculations are performed locally in your browser using JavaScript. No data — including age, weight, height, or gender — is transmitted to any server, stored in cookies, or logged in any way. The information you enter exists only in your browser window while the page is open.