Per capita water use is crucial for understanding how much water a municipality uses and planning water supply systems. Previous methods for estimating per capita water use in Japanese studies have been found to be inadequate. A case study in IchiharaShi, Chiba Prefecture, showed that municipal water demands depend on residential users and big water consumers like public baths and industries. It is important to separate these two types of users when estimating per capita water use. The study concluded that estimating per capita water use based on residential water usage is essential for accurate planning.