A new method is introduced for calculating the shape of a gear hob for generating gears with an arbitrary tooth profile. This is applicable to calculate the shape of the tooth profile generated by a hob with an arbitrary shape of the cutting-edge. Because this method simulates exactly the metal removing process in gear tooth profile generation, it is possible to calculate the generated tooth profile when an interference occurs between the cutting edge and the finished tooth profile. As an example, the shape of the cutting edge of a hob was calculated for cutting cylindrical gears with a circular-arc tooth profile (Novikov gears). The profile errors produced in the calculation were less than 1 μm for gears with a module of 5 mm.