A new methodology for probabilistic life prediction is proposed in this paper. Short crack growth is included into the proposed methodology using the equivalent initial flaw size (EIFS) concept. The proposed methodology is based on the Kitagawa-Takahashi diagram and only uses fatigue limit and fatigue crack threshold stress intensity factor. Unlike the commonly used back-extrapolation method for EIFS calculation, the proposed methodology is independent of applied load level and is very efficient in calculating the statistics of EIFS. The advantage of the developed EIFS concept is that an accurate fatigue life prediction can be obtained without complicated micro-mechanics analysis of small crack growth. The developed EIFS methodology is combined with probabilistic crack growth analysis to predict the fatigue life distribution of smooth specimens. Model predictions are compared with experimental observations for various metallic materials.