Two types of disc motors are investigated in the paper: - with salient poles, where armature core is made of ferromagnetic steel, as shown in Fig. 1, - with coreless armature and two-layer winding as shown in Fig.4. Dependence of rotating torque on number of pole pairs p and ratio of inner diameter d to outer diameter D (β=d/D) has been determined for salient-pole motors (Fig.3). Basing on these characteristics, the motor's rated power has been calculated depending on motor's dimensions. The results are set out in Table 1. In case of coreless armature motor the basic dependencies between motor dimensions and electromechanical parameters have been given. Using these relations, armature dimensions have been calculated for 3 kW, 180 V, 2000 rpm motor. The described methodology of calculating armature magnetic circuit dimension and winding data constitutes first design phase of disc motor. During second design phase the motor should be optimised and its magnetic circuit calculated e.g. by some field method.