High demand and consumption rates of ecological materials and services to satisfy societal needs and for the dissipation of emissions are quickly exceeding the capacity that nature can provide. To avoid a tipping point situation, where ecological services may no longer be available, society must consider a sustainable path forward. The chemical industry's response is to incorporate a sustainability approach early into process design to reduce the quantity of goods and services needed and to prevent and minimize releases, while increasing their economic and social benefits. This approach leads to design modifications of existing and new chemical processes, which requires a complete sustainability performance assessment that can support a decision-maker to determine whether a process is becoming more or less sustainable. Hence, the development of indicators capable of assessing process sustainability becomes crucial. This work presents a taxonomic classification and definition of sustainability indicators according to the environmental, efficiency, energy, and economic bases proposed by the GREENSCOPE methodology for the evaluation and design of sustainable processes. In addition, this work proposes a general scale for measuring sustainability according to the identification and use of best possible target and worst-case scenarios as reference states, as the upper and lower bounds of a sustainability measurement scale. This taxonomy will prove valuable in evaluating chemical process sustainability in the various stages of design and optimization.