In this retrospective analysis of CT scan images from a group of prospectively enrolled patients with progression of traumatic cerebral hematoma, we asked whether there is a difference in volumes measured between the conventional ABC/2 formula and a semi-automated computer software, 3D-Slicer. We found that the conventional ABC/1 formula demonstrated a high degree of variability with a clinically significant mean difference in hematoma volume between readers. Additionally, when hematoma volumes were large, there was more variability in the measurements suggesting 3D-Slicer measurements might be more consistent in larger hematomas.