The goal of this research is to determine which surface roughness metrics are the most important for predicting fatigue in Metal Additive Manufacturing (3D printing). A Keyence Optical Scanning Microscope was used to measure surface roughness metrics. The researcher studied literature to improve his understanding of the metrics and their relevance to fatigue. In addition, a Measurement System Analysis was performed to measure the repeatability of the researcher’s measurement procedure. Knowing which metrics are the most important will help manufacturers identify parts that are at risk of fatigue failure, before they reach the end-user.