Skeletal estimation methods to reconstruct the juvenile biological profile are largely limited to those estimating age and, to a lesser extent, sex. While body mass is not generally estimated as part of the biological profile in forensic investigations, this is a logical candidate for inclusion in the forensic biological profile, as it has long been of interest in paleoanthropology and several methods to estimate juvenile body mass currently exist. To explore the performance of body mass estimation for juveniles, the authors tested the accuracy and precision of previously published panel regression formulae using two femoral measurements: the breadth of the distal metaphysis and the cross-sectional polar moment of inertia (J). The test sample consisted of measurements of 94 individuals from birth to 12.5 years of age, taken from postmortem computed tomography scans housed at the Office of the Medical Investigator, New Mexico, USA. Results indicate that body mass estimates are more accurate when estimated from cross-sectional than from metaphyseal measures. Both formulae, however, consistently underestimated weight, and the magnitude of the underestimation increased exponentially with age. This suggests that, contrary to what others have argued, body mass estimation is complicated by population variation in body composition. This study reinforces the importance of documenting and investigating the ontogeny of human variation. The global increase in medical imaging in clinical settings can be leveraged to obtain skeletal data for juveniles from a wide range of ontogenic environments, marking an exciting time for the study of human variation.