The bounce average Fokker-Planck equation describing fast particles in a tokamak with toroidal magnetic field ripple has been solved numerically by a Monte Carlo approach. The essential element is that the ripple effect is treated as a diffusion of banana trapped particles. The diffusion coefficient is precalculated from a semi-analytical expression for a given plasma geometry. The kinetic equation is solved for the processes of fast particle slowing down, pitch angle scattering, ripple diffusion and acceleration by ion cyclotron resonance heating. This approach was found to be particularly useful for the study of fast particle behaviour in non-stationary conditions, including sawtooth effects. A ripple loss code has been developed on the basis of this principle. The code has been benchmarked against a full orbit following Monte Carlo code. Applications of the code to the experimental results from the JET experiments with 16 and 32 toroidal field coils are given