We propose a fracture mechanics based method for determination of equivalent initial damage size (EIDS) distribution in as-built additively manufactured (AM) Ti-6Al-4V notched geometries. The crack growth model is shown to correctly capture the effect of the stress raisers and load ratio on the fatigue life of notched specimens. Results of constant amplitude fatigue tests on notched round bar specimens, with two different stress concentration factors and at multiple load ratios, are fitted to a three-parameter Weibull distribution. Based on the surface roughness measurements performed in this study and in the literature, maximum surface valley depth is found to be a reasonable estimation of the median EIDS.