The method, step by step
- Average the mother's and father's heights to get mid-parent height.
- Round the child's age to the nearest half-year and look up that row of coefficients for their sex.
- Multiply height (inches), weight (pounds) and mid-parent height (inches) by their coefficients and add the intercept.
- The sum is the predicted adult height in inches. Apply the method's error to get a range.
Where the coefficients come from
Khamis and Roche fitted the model to the Fels Longitudinal Study: 223 boys and 210 girls from southwest Ohio, measured every six months until they stopped growing. Earlier methods (Roche-Wainer-Thissen, Bayley-Pinneau) needed skeletal age from a hand X-ray. Khamis-Roche replaced it with weight and mid-parent height, so anyone with a tape measure and a scale can use it.
This calculator uses the erratum-corrected coefficients and snaps age to the nearest half-year, the same way the TallPath app does. It runs in your browser; nothing is sent to a server.
How weight enters the prediction
At most ages the weight coefficient is small and negative: two children of the same age and height, the heavier one tends to be further through puberty with less growth left. That is why the calculator asks for weight even though weight itself doesn't make anyone taller.
