The calculation of losses is highly required to design any superconducting device. To do that the analytical approach is the best way in term of parameter analysis. Bean_s model is based on the fact that the resistive transition is sudden. This assumption is more suitable for low critical temperature superconductors. For ceramics, the transition is smoother, so the variation of electric field E with current density is a function well approached by kJn. Using this kind of function and a dimensional analysis the authors propose a new analytic formula to calculate the losses in the case of incomplete penetration of current. Calculated results are compared to measured ones and the validity limit is shown.