Detailed anamnesis and systematic physical examination are often relevant in the diagnostic routine of acute appendicitis. However, physicians are increasingly motivated to obtain radiological approval. Inherent limitations due to radiologists' experience and the presenting anatomy may result in contradictory outcomes between the described and intraoperative findings. In this study, a comparison of anthropometric measurements of the appendix vermiformis obtained by radiologists and surgeons in children with acute appendicitis is discussed. The external appendiceal diameter in 53 patients who underwent surgery between April 2022 and January 2024 was measured at three different anatomical locations during preoperative ultrasound and intraoperatively with the help of Vernier calipers. Appendectomy materials were classified into negative, acute, and complicated appendicitis subgroups on the basis of histopathological results. The widest median diameter, expressed in millimeters, was analyzed statistically in terms of diagnostic accuracy. Histopathological analysis revealed negative appendectomy in 15.1%, acute appendicitis in 66%, and complicated appendicitis in 18.8% of the patients. The median age at presentation was 11.4 years (4–17.3 years), and 45.3% of the patients were females. The average median appendiceal diameter was 7.8 ± 2.4 mm according to the caliper and 7.9 ± 2.7 mm according to ultrasound (p > 0.05). The evaluation by the caliper revealed a much smaller diameter in 19 patients than did ultrasound. The appendiceal diameter of eight documented negative appendectomy samples was 7 mm or greater. US failed to identify the presence of an appendicolith in 11 cases (20.8%), all of which were disclosed during histopathological evaluation. It is possible to conclude that ultrasound and intraoperative anthropometric measurements correlate according to our study. Diagnostic accuracy, however, which is individually based on ultrasound appendix diameter values greater than 6 mm, is controversial. It is clear that comparison and further reinterpretation of such anthropometric measurements in light of histopathological consequences may help diminish the frequency of negative and perforated appendectomies.