T The upstream oil-gas (oil and gas) industry is an energy production sector that has a major contribution to the domestic economy, but also requires a very large amount of capital. The casing tubing industry is one of the mandatory contributors in upstream oil and gas activities. The Indonesian government stipulates that all stakeholders in the upstream oil and gas industry must play an active role in increasing the use of domestic products. The use of domestic products is represented in the form of the achievement of the TKDN value which is expected to be a tool for measuring the progress of the industrial ecosystem. However, currently the existing calculation system has not been able to represent the condition of the industrial ecosystem. Therefore, it is necessary to conduct a study to develop a TKDN calculation system to be able to represent the industrial ecosystem, especially the casing tubing industry. This research methodology consists of several stages, namely stage 1 is the formulation of the problem, literature study, determination of model logic, problem boundaries and research benefits, formation of a framework of thought and stages of research. The second part is data collection and in-depth expert interviews. The third part is to analyze the gaps, strengths, and weaknesses of the existing system. The fourth stage is the calculation of the weight of the TKDN critical factor using the entropy method. The fifth stage is the preparation of the TDKN hitting scheme and tools, model verification and validation. The result is the development of a specific TKDN calculation model for the casing tubing industry which has a limit in the form of a critical factor weight. The development of this model is manifested in the form of a TKDN calculator which is simpler and able to represent the casing tubing industry ecosystem.