In magnetic recording, the field configuration of the writing head is of major importance, but it is difficult to measure its actual strength. This paper describes a method of determining both the field geometry of a head and the field strength by using tapes of various coating thicknesses. By differentiating the magnetic flux with respect to the thickness, remanence curves are obtained. These curves may be compared to the remanence which was measured statically. This way, the oersteds of the head field can be determined in a much closer vicinity to the head gap than by previously described methods.