We report on two numerical approaches to quantify mixing-method I is based on kinematic mixing rates (i.e. the mixing, rates due to the fluid mechanics only) and method II is based on the evolution of the concentration distribution of a passive tracer. For method I, kinematic mixing rates are established from the way infinitesimal fluid line elements are stretched by the flow and. from method II, the mixing rate is determined from the rate at which the variance of the concentration of a particle cloud decreased. during the mixing process. For method II, concentrations were calculated by tracking a large number of diffusive particles using a Langevin-type equation (i.e. introducing a random walk term to model molecular diffusion) and by dividing the domain into small regions. The two approaches were applied to a case study, oscillatory flow mixing (OFM) within baffled tubes, which is an inertial flow that has been shown to provide an efficient alternative to conventional mixing processes and is a viable candidate for technological application. A numerical solution for this flow field was calculated by solving the full axisymmetric Navier-Stokes equations which is valid up to a value of the oscillatory how Reynolds number of order 200. The results of the two mixing methods are compared and their applicability and usefulness in the characterisation of the mixing ranked. The effect of fluid oscillation conditions are also quantified, for the flow field examined.