Hi, I am currently writing my dissertation on the effects of Sports Supplements on Body Fat % and the comparison of tools as a measure. I have thoroughly enjoyed using your website as a source and was interested how your body fat % calculator works. The skinfold calculator identifies both 3 and 7 site calculators BUT I have found many websites and equations require waist and forearm circumferences. Could you please explain how that is not required by your calculator. If possible any reading on this matter would be greatly appreciated. I look forward to your response. Once again a great resource!
These formulas have been around for many decades. The references are provided near the bottom of the mentioned calculator. You can look at those studies up on PubMed. They will give you a comprehensive understanding of the science involved in these formulas.
When I was in college (KSU), many soldiers from Fort Riley, who were considered overweight when measured by circumference measurements, would set appointments with our lab and pay money to have their body composition (with lung volume) tested because it was much more accurate than measuring girths as they do in the Army. But obviously, that requires a specialized laboratory equipment, and a higher level of expertise to administer such tests.
In a clinical setting, skinfold measurements offer a more practical alternative in estimating body composition and is more accurate thAn the alternatives like bioelectrical impedance, near infrared, ultra-sonic, MRI, and circumference measurements, etc. In my experimental methods class, I also conducted a study comparing skinfold measurements with a formula using waist circumference in college men who weight trained. In this study, we found that if men had an enlarged musculature of the midsection (i.e. developed Erector Spinae, Obliques Rectus Abdominis), that circumference measurements would under estimate lean body weight therefore increasing the estimated percent body fat.
In a clinical setting, you will need to look at the changes of body composition occurring over time since there is a degree of measurement error with skinfold and even circumference measurements. For this reason, these indirect measurements have not been considered accurate enough for academic research examining body composition cha nges over time. Wilmore, et. al. (1970).
You can also do more research in this area on PubMed.
Wilmore JH, Girandola RN, Moody DL (1970). Validity of skinfold and girth assessment for predicting alterations in body composition, Journal of Applied Physiology, 29 (3), 313-317.