For kids between the ages of eight and 16, three measurements -- standing height, sitting height, and weight -- can be used to estimate how long before the growth spurt, Dr. Baxter-Jones said. Since it's known that at the growth spurt, a child will have attained 92% of his or her adult height, it's then possible to calculate the final height.
The method takes into account the biological age of the child, designating him or her as early-, average-, or late-maturing, depending on when the growth spurt is expected.
It's accurate to within 2.1 inches 95% of the time in boys and to within 2.68 inches 95% of the time in girls, the researchers reported.
A calculator is available online here. But, the test has only been validated with healthy white boys and girls (the investigators who developed the formula are in the Canadian West), so YMMV.