This note presents the development of a scale-up correlation of single-phase axial dispersion coefficients in both batch and continuous oscillatory baffled flow systems. A hydraulic diameter is introduced to relate axial dispersion coefficients for various baffle geometry, including close-fit and loose-fit baffles, Karr plate and multiperforated plate, and various rates. The significance of this note is that the mixing characteristic in oscillatory flow devices is linear.