This paper describes a tool designed to assess the machine translatability of English source texts by assigning a translatability index to both individual sentences and the text as a whole. The tool is designed to be both stand-alone and integratable into a suite of other tools which together help to improve the quality of professional translation in the preparatory phase of the translation workflow. Assessing translatability is an important element in ensuring the most efficient and cost effective use of current translation technology, and the tool must be able to quickly determine the translatability of a text without itself using too many resources. It is therefore based on rather simple tagging and pattern matching technologies which bring with them a certain level of indeterminacy. This potential disadvantage can, however, be offset by the fact that an annotated version of the text is simultaneously produced to allow the user to interpret the results of the checker.