X-ray computed tomography (XCT) is a widely adopted nondestructive technique for characterizing internal porosity in additive manufactured (AM) components. However, the accuracy and precision of porosity characterization using XCT can be affected by factors, such as XCT system configuration and post-processing methodologies. This study investigates the influence of these variables on porosity characterization by comparing results obtained from four different XCT systems and two distinct analysis workflows applied to a single metallic AM sample. A benchmark is also established for the XCT performance by using a high-resolution reference dataset generated through mechanical polishing serial sectioning (MPSS). Porosity metrics, including volume fraction, pore count, size distribution, and equivalent spherical diameter (ESD), were computed for large pores ( $ge 84~mu $