We have been engaged in developing a readability index and its application software attuned for Japanese EFL learners. The index program, Ozasa-Fukui Year Level Program, Ver. 1.0, was used in developing the readability metric Ozasa-Fukui Year Level Index but tended to assume a high level of computer knowledge in its users. As a result, the application proved to be difficult to operate for 'lay' users. Since the majority of its expected users are not computer specialists, it is of crucial importance to develop a user-friendly program that can be used easily without any professional knowledge or skills. The goal of the present study was to provide a readability application that was informed by our index development work and sufficiently user-friendly for use by EFL professionals, i.e., Ozasa-Fukui Year Level Program, Ver. 2.0. The present paper describes the background context in which this work was undertaken and details our approach both to readability measurement and to the design of this software application for assessing readability in the Japanese EFL context.