In this work a new magnetometer setup and a novel model based data evaluation technique was used to determine the creep damage in ferritic power plant steel. The tested material was 1Cr-0.5Mo-0.25V ferritic steel which is commonly used as pipeline base material of steam generators in power plants. It is commonly accepted that a combined form of fatigue and the creep processes cause the deterioration of this structural parts due to long time elevated temperature service. Nowadays, there is increasing need for remaining lifetime estimation of these engineering structures. In this paper, the variation of magnetization curves of Cr-Mo-V ferritic steel due to creep measured and the relation between creep damage and the magnetic property changes is discussed. A new data evaluation technique is presented which is based on the hyperbolic model of magnetization. A magnetic descriptor was derived from the hyperbolic model which can be determined from the initial part of the normal magnetization curve. The introduced parameter and evaluation technique seems to be especially useful for magnetic nondestuctive remanent lifetime evaluation.