Speakers frequently retrace one or more words when continuing after a break in fluency. Syntactic principles constrain the points from which speakers retrace; however syntactic principles do not provide predictions about the relative usage of different allowable retrace points. Such predictions are useful for automatic processing of repairs in speech technology, particularly if they use information readily available to a speech recognizer. We propose a quantitative model that predicts the overall distribution of retrace lengths in a large corpus of spontaneous speech, based only on word position. The model has two components: (1) a constant, position-independent probability for extending a retrace by one more word; and (2) a position-dependent probability to “skip” to the beginning of the sentence. Results have implications for modeling repairs in speech applications and constrain explanatory models in psycholinguistics.