Investigation of the driving capability of a microactuator used in hard disk drives (HDD) is essential to ensure that the head is moved to the desired track under a certain voltage. This paper presents three different approaches to calculate the driving torque in a rotary electrostatic microactuator, namely analytical methods, the finite element method (FEM) and the boundary element method (BEM). The torque is roughly calculated using the simplified analytical model first, and then the results are compared with those obtained from FEM and BEM software. This study shows that the simplified analytical model is feasible in the preliminary design stage.