The substantial contribution of the global construction sector to greenhouse gas emissions underscores the urgency of mitigating its environmental impact. This study addresses the pressing need for sustainable practices in the construction sector, focusing on the intricate relationship between concrete grade selection, bridge span length, embodied carbon, and construction costs within a concrete T-girder highway bridge design. By examining various girder spacings, concrete grades, and bridge spans, this study aims to provide holistic insights into material optimisation for structural efficiency, sustainability, and economic viability. Notably, the findings reveal a nuanced understanding of design parameters, with shorter spans exhibiting minimal sensitivity to girder spacing and concrete grade, whereas longer spans highlight their significant role in shaping embodied carbon and cost. The results also show a remarkable similarity between the C25/30 and C32/40 concrete grades, emphasizing the need for a strategic balance between environmental and financial performance. This study underscores scientific rigour and methodological robustness, providing useful contributions to the field of sustainable construction practices. In conclusion, this research advocates a balanced approach that integrates concrete grade, girder spacing, and span length considerations to optimise sustainability and economic feasibility in concrete T-girder bridge designs. These insights facilitate informed decision-making, aligning with evolving trends towards environmentally conscious infrastructure development.