Purpose: A widely used theory of the computational structure of life cycle assessment (LCA) has been available for more than a decade. The case of environmental life cycle cost (LCC) is still less clear: even the recent Code of Practice does not specify any formula to use. Methods: This paper does not aim to resolve all the issues at stake. But it aims to provide an explicit and transparent description of how to calculate the life cycle cost (in whatever way defined), and the value added across the life cycle. Results and discussion: The expressions obtained can be fed into the formulas for eco-efficiency, so that an explicit and reproducible eco-efficiency indicator can be calculated. Conclusions: The results are useful for developing life cycle sustainability analysis, combining LCA, LCC, and social LCA.