Growth Percentile Infant Calculator
Child Growth Percentile Calculator works out Percentile and Z-score (SD score) from Growth reference, Chart and Sex. The default figures on this page give percentile of 90.0 %; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
4 steps
- Chart: CDC Stature-for-age, 2 to 20 years (boys).
- Reference parameters at 96.5 months: L = 0.45526751, M = 128.12371, S = 0.04512709.
- z = ((X/M)^L - 1)/(L*S) = ((135.6504/128.12371)^0.45526751 - 1)/(0.45526751 x 0.04512709) = 1.281552
- Percentile = Phi(z) x 100 = 90%.
Reference percentile curve at this agetable
| percentile | value | unit |
|---|---|---|
| 3 | 117.5 | cm |
| 5 | 118.805 | cm |
| 10 | 120.83 | cm |
| 25 | 124.256 | cm |
| 50 | 128.124 | cm |
| 75 | 132.056 | cm |
| 90 | 135.65 | cm |
| 95 | 137.827 | cm |
| 97 | 139.25 | cm |
Every chart these inputs supporttable
| chart | measure | value | zScore | percentile |
|---|---|---|---|---|
| Stature-for-age, 2 to 20 years | height-for-age | 135.65 | 1.2816 | 90 |
Figures from CDC and WHO growth charts, checked 31 August 2026. Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed · how reference data is kept current
Sources and references
6 sources
What the Child Growth Percentile Calculator calculates
Computes a child's growth percentile and z-score for height, weight, BMI, head circumference or weight-for-length against the CDC 2000 growth charts or the WHO child growth standards.
How to use this Child Growth Percentile Calculator
Enter Growth reference, Chart, Sex and Units. Percentile updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Percentile, Z-score (SD score) and Reference median for age.
The method follows CDC 2000 Growth Charts - percentile data files with LMS parameters, Kuczmarski RJ et al., 2000 CDC growth charts for the United States: methods and development. Vital Health Stat 11(246), WHO Child Growth Standards - expanded z-score tables (0-5 years), Cole TJ, Green PJ. Smoothing reference centile curves: the LMS method and penalized likelihood. Stat Med 1992;11:1305-19 and CDC, Growth Chart Training: using the WHO growth standards for children under 2 years.
CDC stature-for-age, boy at 96.5 months, on CDC's own 90th percentile curve example
With Growth reference: cdc, Chart: height-for-age, Sex: male, Age: 96.5, the calculator returns Percentile: 90, Z-score (SD score): 1.28155157. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Percentile, Z-score (SD score) and Reference median for age. The inputs you can vary are Growth reference, Chart, Sex, Units, Age and Age unit.
Understanding Percentile, Z-score (SD score) and Reference median for age
A growth percentile is a screening number, not a diagnosis. Serial measurements plotted over time, taken with calibrated equipment, are what a clinician interprets. Discuss any concern with your paediatric provider.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
What is a normal growth percentile for babies?
Computes a child's growth percentile and z-score for height, weight, BMI, head circumference or weight-for-length against the CDC 2000 growth charts or the WHO child growth standards. On this page it is computed from Growth reference, Chart and Sex and shown as Percentile, Z-score (SD score) and Reference median for age.
What percentile is 9 lbs at 2 months?
It needs Growth reference, Chart, Sex, Units, Age and Age unit. Nothing else is required, and the figures stay in your browser.
Is 92 percentile a big baby?
Computes a child's growth percentile and z-score for height, weight, BMI, head circumference or weight-for-length against the CDC 2000 growth charts or the WHO child growth standards. On the figures this page opens with — age 96.5 and height or length 135.6504 — the percentile is 90%. Put your own figures in their place and the working updates beside the result.
What information do I need for the Child Growth Percentile Calculator?
You need Growth reference, Chart, Sex, Units, Age, Age unit, Height or length and Weight. The page opens with default figures that give percentile of 90.0 %, so you can see the scale before entering your own.
What does this Child Growth Percentile Calculator show?
It shows Percentile, Z-score (SD score), Reference median for age, Percent of median, Chart used, Reference, Measurement used and BMI, with the working and any warnings for your entries.
Can I check how the Child Growth Percentile Calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.