This study aims to determine the challenges faced by mathematics teacher-candidates on unit conversion and dimensional analysis. The research was conducted using content analysis method of qualitative research methods. The study group consists of 66 people, 50 females and 16 males, elected through appropriate sampling method, studying at state university in the academic year of 2015-2016. Five open-ended questions were used, prepared by researchers also utilising from the technical literature for the purpose of identifying challenges faced by students during the transfer of mathematical knowledge about unit conversion and dimensional analysis in physics classes. Findings obtained for increasing the validity and reliability of the research were independently coded by each researcher, then these codes were grouped under the same theme of unit conversion and dimensional analysis. Following an investigation on the answers given by students participating in this research, it was determined that they did not have enough knowledge on base quantities within SI unit system and they had problems in transitions between upper and lower coefficients. It was also found that they had misconceptions on the theme of dimensional analysis. Amplitude of mathematical procedures and formulae within physics and the lack of mathematical skills of the students indicates that they suffer an inadequacy in unit conversion and dimensional analysis operations.