This study investigates the relationships between the chemical characterisation parameters of eight switchgrass cultivars grown in Türkiye and their practical yields of ethanol and methane, using Pearson correlation and principal component analysis (PCA). Acid-insoluble lignin, cellulose, and total Kjeldahl nitrogen (TKN) showed moderate positive correlations with methane production, while proteins, acid-soluble lignin, and lignin had minimal influence. BoMaster exhibited the highest glucose content (41.0 %) in the second harvest, while Trail Blazer and Kanlow also showed elevated glucose levels, indicating strong ethanol production potential. The Cave in Rock cultivar yielded the highest methane output, at approximately 250 mL CH4/g VS, whereas Kanlow demonstrated superior ethanol potential, estimated at 75 L ethanol/tonne switchgrass. Methane production positively correlated with acid-insoluble lignin and cellulose content, while reducing sugars, elemental carbon, and total sugars strongly correlated with ethanol production. Cellulose and hemicellulose, however, showed weak correlations, suggesting that pre-treatment may enhance sugar release. PCA revealed that the first four principal components accounted for 84.7 % of the overall variance in ethanol production, with reducing sugars, carbon, total sugars, hydrogen, and proteins positively associated with the first component. This study fills a gap in the limited literature on the relationship between switchgrass characterization and its potential for bioethanol and biogas production, providing insights to optimize switchgrass as a renewable energy source.