Methodology
How GrowTall turns references into insight
No proprietary magic, no black boxes. GrowTall converts published growth science into understandable, longitudinal insight — and says exactly where the limits are.
GrowTall is built exclusively on established, published growth references — WHO Child Growth Standards, CDC 2000 charts, CDC BMI-for-age, the mid-parental target height and the Khamis-Roche model — and converts them into understandable insights without presenting estimates as diagnoses or guarantees.
The references we build on
| Reference | Applies to | What it gives GrowTall |
|---|---|---|
| WHO Child Growth Standards | Birth – under 2 | Length-for-age percentile curves for infants |
| CDC 2000 Growth Charts | Ages 2 – 20 | Height-for-age percentiles and curves |
| CDC BMI-for-Age | Ages 2 – 20 | Body-composition context with optional weight |
| Mid-parental target height | Growing children | Genetic target corridor from parental heights |
| Khamis-Roche model | Growing children | Adult-stature estimate without bone-age X-ray |
How percentiles are computed
For a given age and sex, GrowTall locates the adjacent points in the reference dataset and interpolates between the published percentile curves (for example P3–P97) to place a measurement on a continuous 0–100 scale. Percentiles are always computed against the age-appropriate reference — WHO under age 2, CDC 2000 from age 2.
How growth velocity is computed
Velocity is the height change between two measurements divided by the elapsed time, expressed in centimeters per year. Pairs taken less than 14 days apart are normalized so that normal daily height variation (about 1–1.5 cm from spinal disc hydration) never masquerades as a growth signal.
How estimates are framed
The mid-parental method yields a genetic target with a ±8.5 cm corridor. The Khamis-Roche model yields a predicted range from age, height, weight and parental heights. GrowTall always displays both as ranges on a visual scale — never as single guaranteed heights — and labels them as estimates.
Editorial principles
- Cite the source. Every method in the app maps to a published reference.
- Corridors over pinpoints. Estimates are ranges; the trend is the story.
- No sensationalism. No miracle-growth claims, no fear-mongering, no supplement marketing.
- Screening context, not diagnosis. Patterns that merit attention are described with a path to a professional, never with alarm.
- Honest privacy language. Local-first storage, optional coarse analytics, no ads, no health-data selling — described exactly as it works.
Primary sources
- WHO Multicentre Growth Reference Study Group. WHO Child Growth Standards. Acta Paediatrica, 2006.
- Kuczmarski RJ, et al. 2000 CDC Growth Charts for the United States. National Center for Health Statistics.
- Khamis HJ, Roche AF. Predicting adult stature without using skeletal age: the Khamis-Roche method. Pediatrics, 1994.
- Tanner JM, et al. Standards for children's heights at ages 2–9 years — the mid-parental tradition in pediatric height assessment.
GrowTall implements these published methods for personal tracking and education. It is not a medical device, does not provide diagnoses, and its estimates are not a substitute for professional evaluation.
Common questions
Is GrowTall clinically validated?
GrowTall implements published, widely used reference methods faithfully. The app itself is a consumer tracking and education tool — not a medical device — and its outputs are screening context, not clinical findings.
Will the methodology change over time?
The references are stable and widely adopted, and any future updates to the underlying datasets would be documented here. The principles — corridors, citations, honest limits — do not change.
Why does GrowTall refuse to give exact height predictions?
Because no method can. Individual variation around any model is real, and honest ranges are what pediatric practice itself uses. Certainty would be marketing, not science.
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