Calculator
Example data table
| Age (months) | Sex | Weight (kg) | Height (cm) | BMI | BMI percentile |
|---|---|---|---|---|---|
| 6 | Male | 7.9 | 67.6 | 17.29 | 49.7th |
| 18 | Female | 10.2 | 80.7 | 15.66 | 35.4th |
| 48 | Male | 16.3 | 102.3 | 15.58 | 52.1th |
Formula used
- BMI = weight(kg) ÷ height(m)2.
- LMS z-score (when L ≠ 0): z = ((X/M)L − 1) ÷ (L·S).
- LMS z-score (when L = 0): z = ln(X/M) ÷ S.
- Percentile = NormalCDF(z) × 100.
- Percentile curve value: X = M·(1 + L·S·z)1/L (or M·eS·z when L = 0).
How to use this calculator
- Enter sex, age (dates or months), and measurements.
- If the child was preterm, enter gestational age.
- Choose corrected age if you want that adjustment.
- Select the metrics you want, then press Submit.
- Review z-scores, percentiles, and the interpretation band.
- Use Download CSV or Download PDF for sharing.
FAQs
1) What do percentiles mean?
A percentile compares your child to a reference group of the same age and sex. For example, the 60th percentile means the measurement is higher than about 60% of peers.
2) What is a z-score?
A z-score expresses how far a measurement is from the reference median, measured in standard deviations. It helps when tracking small changes over time and comparing different metrics.
3) Why is corrected age offered?
For children born early, corrected age adjusts for weeks of prematurity. Many clinicians use corrected age for growth interpretation until about 24 months, depending on local practice.
4) Why upload an LMS CSV?
Accurate percentiles require the reference LMS parameters for each metric, age, and sex. Uploading an official LMS dataset lets this calculator match your preferred standard and improves reliability.
5) Which metrics are included?
This tool can compute weight-for-age, length/height-for-age, BMI-for-age, and head circumference-for-age. You can enable or disable any metric using the checkboxes.
6) Can I use pounds or inches?
Yes. Weight can be entered in kilograms or pounds, and length/height or head circumference can be entered in centimeters or inches. The calculator converts everything to metric internally.
7) Why do I see “No LMS data”?
That message appears when the selected metric is missing from the active LMS dataset, or the age is outside its range. Upload a dataset that includes the metric and the child’s age range.
8) Is this a diagnosis tool?
No. Percentiles and bands are screening-style summaries. Clinical context matters, including feeding history, parental size, and medical conditions. Use the results to support discussions with a qualified clinician.