Abstract In the Emergency Department (ED) actual body weight (ABW) is essential for accurate drug dosing. Frequently, the ABW is unknown and direct measurement troublesome. A method using the mid-arm circumference (MAC) to estimate ABW has been developed and validated in the United States of America (USA). This study aimed to validate the MAC-formula for estimating ABW in the Dutch population and compare its performance within the American population. Data were obtained from the Dutch National Institute for Public Health and the Environment (RIVM) and extracted from the American National Health and Nutrition Examination Survey (NHANES) datasets. We included all subjects’ ≥70 years whose MAC and weight were recorded and obtained additional anthropometric data. We used the equation: kg = 4 × MAC-50 to estimate the ABW of all subjects and compared results. We retrieved 723 and 972 subjects from the Dutch and American dataset, respectively. The MAC is better correlated with ABW in the American dataset when compared with the Dutch dataset (Pearson r = 0.84 and 0.68, respectively). Bland-Altman bias was –7.49 kg (Limits-of-Agreement [LOA] –27.5 to 12.27 kg) and –0.50 kg (LOA –20.99 to 19.99 kg) in the Dutch and American datasets, respectively. The MAC based formula to estimate ABW is a promising tool for the elderly American population. However it is not accurate within the Dutch elderly ED population. Consequently, it is not applicable to Dutch EDs. This study highlights that the results of anthropometric studies performed within the USA are not per se generalizable to the European population.