A better definition of the long term protection strategies against littoral hazards requires evaluating investment, management, and maintenance costs of various interventions on levees and other civil engineering structures, as well as on beaches and dunes. The cost study of coastal protections (Cerema 2018) aims at providing the assessment of the project global cost. Based on the study of a large number of projects completed in France, estimations were produced to enhance the reliability of these calculations at the scale of a site in the littoral zone or of an individual natural or artificial structure. For each structure type, the obtained results are essentially linear, surface, volume or mass costs (initial costs or annual average costs), as well as lifetime and intervention frequency. To obtain this information, the analysis mainly consisted of: • the creation of a typology which crosses « structure type » and « intervention type » which allows establishing homogeneous groups of characteristic operations; • the identification, for every group, of physical parameters influencing the associated costs, which allows the user of the manual to evaluate better the difference between the observed high and low values. This paper presents the context of the study, its methodological process, the progress of the investigations and the analyses, the obtained results, and finally the generic lessons learned.