The relation between the welding conditions and welding distortions were studied with the weld parameters, current, welding speed and plate thickness, and the form of the distortions were derived theoretically. To derive these formulas, the temperature distribution on the plane normal to the direction of the weld line was assumed to be parabolic. Both the theoretical studies for the transverse shrinkage and angular distoction were compared with the experiments. The experiments were performed on the fundamental cases of a bead welds on rectangular mild steel plates. It was found that the distoction formulas were in good agreement with the results of the experiments. The formulas for the calculation of the distortion were established for the case of bead on plate weld using rectangular mild steel plate and the KS E4313, $4mmphi$ welding rod.