The analytical formulae of the magnetic field, the vector potential and the inductances of long helical conductors with an arbitrary pitch are given as a unified scheme from a helical solenoid to a straight conductor. It is also shown that the obtained expressions are consistent with the well-known expressions for a closely wound helical solenoid and a straight conductor in both limits of the infinitesimal and infinite twist pitches, respectively. In addition, the right-handed and left-handed long helical conductors are clearly treated for this unified scheme.