This paper presents TransDic, a free distribution tool for the phonetic transcription of word lists in Spanish and Catalan which allows the generation of phonetic transcription variants, a feature that can be useful for some technological applications, such as speech recognition. It allows the transcription in both standard Spanish and Catalan, but also in several dialects of these two languages spoken in Spain. Its general structure, input, output and main functionalities are presented, and the procedure followed to define and implement the transcription rules in the tool is described. Finally, the results of an evaluation carried for both languages are presented, which show that TransDic performs correctly the transcription tasks that it was developed for.