In fishing port and fishing ground construction, the serviced coefficient of the work vessel is a very important factor to calculate the construction cost properly. For important ports in Japan, the serviced coefficient is stipulated with the observation wave height according to the "Service coefficient setting" (1997 Ministry of LIT notification). However, in other harbors, fishing ports and fishing ground constructions, the serviced coefficient is applied mutatis mutandis. But its value is not accurate. In this study, the authors built a web application that calculates the service coefficient. In the web application, the serviced coefficient is calculated with wave height, rainfall, and wind speed for a specific period. It was clarified that the definition of stormy day and the construction period will cause a difference in the serviced coefficient. In addition, it was clarified that the construction in bad weather conditions greatly increases the serviced coefficient.