The demands for filleted end milling with high efficiency are increasing more and more. Path interval determination is one of the computational processes in the tool path generation, and its development can offer further improvement in multi-axis filleted end milling. However, to our knowledge, the practical approach has been hardly proposed so far. Hence, this study proposes a novel algorithm to determine a suitable path interval in multi-axis filleted end milling with a tool inclination. The procedure with wide applicability and robustness was described based on the 3D geometrical consideration of filleted end mill. Then, the characteristics of procedure were discussed with the visual data obtained from the computational results.