Considering bridges’ long service life and large scale, the decisions made in the design stage have significant impacts on resource consumption and waste generation throughout the life span. Stainless steel has recently been more often adopted as an alternative in structural components. While stainless steel has the advantage of low maintenance requirement, it is expensive and consumes more energy than conventional steel during the production process. The implementation of life cycle assessment (LCA) on stainless steel bridges is rather limited at present. Also, a general LCA requires large amounts of data input and prior knowledge of LCA. It may lead to barriers when architects and structural engineers try to assess the potential environmental performance of bridges in the early design stages. Accordingly, this paper conducts a comparative case study of bridges made of conventional steel and stainless steel with a simplified design-integrated life-cycle analysis tool, which enables users to estimate environmental impacts, life-cycle cost (LCC), and circularity of different design variants and perform optimization. The MATLAB-based tool is based on a parametric model consisting of three main modules, i.e. input, calculation, and output. Time-consuming procedures in LCA are simplified through default assumptions and predefined mathematical equations. Thus, quantitative outcomes of target indicators can be obtained according to the limited input variables and supplementary information from an updatable database. This paper concludes the key design parameters of bridges made of various steels through sensitivity analysis. The simultaneous assessment of LCCs, environmental impacts and circularity provides a more holistic view while assessing the sustainability of bridge construction.