The specific resistance of the plough body (a quotient of its working resistance and furrow cross section) depends on three factors: soil conditions, working speed and plough body shape. The last dependence has not been previously defined analytically. A novel method is being presented in this publication, which allows us to define and calculate the parameters of a plough body influencing its specific resistance, as well as the relationship between these parameters and specific resistance of different plough bodies. The proposed equation includes also soil conditions and working speed. The calculated parameters are based on the dimensions taken from drawing of a plough body working surface through the soil. The knowledge of such a relationship should be very useful in the design of new plough bodies and improvement of existing ones. The dependence between defined parameters and specific resistance has been calculated with statistical methods on the basis of field and laboratory investigations of plough bodies with different working surface shapes. The scope of this investigation covers the cylindroidal, semihelicoidal and helicoidal plough bodies, their working speeds in the range of 0.81 - 2.5 m/s, and soil compactness measured with a cone penetrometer in the range of 1.35 - 1.93 MPa (in field investigations). The introduced relationship has been verified for another 10 ploughs during field investigations, conducted in different soil conditions, at different working speeds.