The pellet particle drift due to the gradient of the magnetic field has a strong influence on the plasma fuelling characteristics. It is directed towards the low field side of the torus and depends on various pellet and target plasma parameters. This phenomenon might play a vital role for the pellet fuelling capability in ITER. Therefore, many efforts are undertaken to analyse it in detail and to improve predictions. A first-principles code for the calculation of the pellet source profile, based on enhanced versions of an NGPS-type ablation and a four fluids Lagrangian drift model, has recently been developed and benchmarked by comparison with drift measurements from the experiment and in full transport simulations. Methods and results are described in section 2. In section 3, scaling laws for the rough calculation of the drift displacement, based on a parameter scan performed with the pellet code, are presented. Section 4 deals with calculations of the drift behaviour in ITER.