Particulate contamination formed by homogeneous clustering reactions of silicon hydrides within silicon chemical vapor deposition processes is an important source of yield loss during semiconductor processing. On the other hand, intentional synthesis of silicon nanoparticles may be of great interest because of the unique optical and electronic properties of nanostructured silicon. Kinetic modeling can play an important role in developing a fundamental understanding of the particle clustering chemistry, and knowledge of the thermochemistry and reactivity of these silicon hydrides is necessary if a mechanistic kinetic model is to be constructed. Experimental measurements of thermochemical properties are usually expensive and difficult, and it is desirable to use computational quantum chemistry as an alternative. In this work, several theoretical methods were used to calculate thermochemical properties of silicon hydrides. Among the methods used, Gaussian-3 theory (G3) using the geometries from B3LYP density functional theory (B3LYP/6-31G(d)), referred to as G3//B3LYP, showed the most promising results with an average absolute deviation of 1.23 kcal/mol from experimental data for standard enthalpies of formation of small (