This paper describes a method to calculate inductances of magnetic switches, toroidal coils wound on ring-shaped cores of non-linear magnetic material. To check the described theory, measurements have been carried out on the inductance of magnetic switches in the saturated state. Most text books give expressions for the inductance, but for the critical applications presented here a better approximation is required. Therefore to calculate the inductance of a toroid, the main and three additional types of flux have been taken into account. As a result of this study, a remarkable agreement between the measured and calculated values is found for a large range of turns. For a toroid with a large number of turns the main flux is large compared to the secondary fluxes. For small numbers of turns however, the main flux and the secondary flux contribute equally to the total flux.