A classical approach to calculate the energy and the orientation of symmetric top and linear molecules in high electric fields is proposed. This calculation is particularly well adapted to large molecules. It is used to simulate the deviation of a molecular beam in an inhomogeneous electric field. We give an example of experimental and calculated profiles of deviation for a transition metal-fullerene compound TiC60. This is the first direct measurement of the permanent dipole of a large rigid molecule in the gas phase.