History of the Khamis Calculator
Dr. Roche worked with researchers on the Fels Longitudinal Study collecting information for personal study and contracted research. The focus of the study was to find predictors that could give some insight into growth rates, final height and final weight in adulthood. After years of research, four factors that contributed to growth were revealed:
- current height
- current weight
- mid-parent height
- skeletal age
With these four indicators, researchers were able to predict, within reason, the height a child would achieve in adulthood. Skeletal age required x-raying the wrist and hand, so this predictor was left out of the final Khamis Calculator.
(Another method used to calculate height is the gray method. Try this one, too!)
The mathematical equation behind the Khamis Calculator started out simply as double the child’s stature at age two. When this method proved unreliable, especially for girls, Roche refined the equation based on the results of the Fels Longitudinal study. The new linear equations were more accurate:
- Males: 22.7 plus 1.37 times height at 2 years
- Females: 25.0 plus 1.17 times height at 2 years
Additional research led to more fine-tuning and the additional of a child’s current weight to the Khamis Calculator.
Limitations to the Khamis Calculator
The Fels Longitudinal Study, which is the research on which the mathematical equations were based, was primarily a Caucasian study. Since the study lacked participation from other races, the Khamis calculator equations are based solely on Caucasian children born to two Caucasian parents.
Gender and genetics account for 70% of growth, the other 30% is based on environment, nutritional factors and illness or disease that may promote or inhibit growth. Some medications have also been associated with slower growth or shorter stature at adulthood, so the Khamis Calculator, though generally accurate, is limited.
There is a margin of error for the results you receive using the Khamis Calculator. For boys, the margin is 2.1 inches and for girls, the margin is 1.7 inches. This means your child could be slightly shorter or taller than the calculator estimates. The margin of error is bigger around puberty and tends to lessen as your child ages past puberty.
The Khamis Calculator can only be used to estimate adult height in children ages 4 to 17.
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