Weight Percentile Calculator
Calculate weight percentile for children and adolescents based on age- and sex-specific references.
What is Weight Percentile?
Weight percentile is a critical pediatric metric. Tracked alongside height, it tells the story of nutrition and overall well-being. Children grow at different rates, but most stay within a narrow band of percentiles over time. Sudden weight changes — either crossing two percentile bands up or down — can signal feeding issues, illness or endocrine problems and warrant clinical follow-up.
How is it calculated?
The percentile is calculated from a z-score: z = (weight − reference mean) / reference SD, where the reference mean and SD are age- and sex-specific approximations of CDC/WHO growth-chart curves. The z-score is converted to a percentile via the normal cumulative distribution function.
Frequently Asked Questions
- Is the 50th percentile the goal?
- No — children should track along their own consistent percentile, whatever that is.
- Should I weigh my child weekly?
- No — monthly is plenty for healthy children.
- Why does weight differ between charts?
- WHO uses breastfed reference data 0–2; CDC mixes feeding methods.
- Does illness affect percentile?
- Yes — short illnesses may temporarily drop weight; recovery typically restores the curve.