Estimating stature of giants from long bones, femur and tibia lengths will often severely under-estimate actual stature using the standard anthropological regression models for tibia, femur — inaccurate for tall or very tall persons, routinely underestimating stature by 6 inches to more than 12 inches!!!
Trotter & Gleser 1952, and Fordisc 2.0 and other commonly used long bone regression models to calculate stature are based on a bell curve using measurements from thousands of skeletons…It works very accurately for persons who are within the normal height range of 5 to 6 feet (1.5 to 1.82 meters). http://www.redwoods.edu/instruct/agarwin/anth_6_stature.htm
However, it becomes increasingly inaccurate the shorter or taller you are from the mean, or normal range!!! That is to say, if you are less than 5 feet tall, or more than 6 feet tall.
Below is a list of 12 different historic and pathological human giants who are from 7 to 8 feet tall and whose bones were housed in museums in the 1890’s, and the dimensions of their long bones listed. The average ratio of femur length to stature of the giant is 1 to 3.73, the femur representing about 27% of living stature.
Using the overly simplistic regression formula such as Trotter and Glesser and Fordisc 2.0, we find that the femurs on the skeleton of the 7 ft 7+ inch 18th century Irish Giant Charles Byrne which measure 62.5 cm (24.6 inches) would erroneously suggest a living stature of only 6 ft 8 to 6 ft 11 inches tall, or fully 8 to 11 inches less than his actual stature!!!!!
Similarly, the Guinness Book of World Records 1990 listed the estimated length of Robert Wadlow’s femur as 29.5 inches (75 cm). Wadlow stood 8 ft 11.1 inches tall in life. Using the Trotter and Glesser or Fordisc 2.0 method, Wadlow should have been only 7 feet 10-1/3 inches tall! – or nearly 13 inches shorter than his actual height of almost 9 feet!
So it becomes rather obvious, that even pathological human giants tend to conform to the same basic proportions as people of normal stature, with some occasional exceptions. But by and large the femur to height ratio generally is from 1: 3.5 to 1:4 in , or 1:3.7 being the general average for males. The ratio tends to be higher in women than in men.
But the general rule of thumb, is that if a femur length is given of any individual, I multiply it by 3.6 or 3.7 to find the approximate conservative estimate of stature. it works very well most of the time for me.