A low-cost mass spectrometer attachment for thermogravimetric analysis has been constructed from readily available commercial instruments and components. The benefits of this set-up include excellent mass-flow repeatability, simple design, and significantly lower adoption cost as opposed to ready-built commercial solutions. The inclusion of an open source software package allows semi-automated, highly simplified data analysis. The results from the instrument show excellent sensitivity for small volumes of evolved gas, as well as highly reproducible signal strengths. The GUI-based software package provides data analysis in a way that is very intuitive and that can be easily modified to work with a broad range of TG instruments. Copyright © 2011 John Wiley & Sons, Ltd.