In one embodiment and method of the present invention, an optical interference fly height (FH) test apparatus for measuring FH is disclosed, in accordance with an embodiment of the present invention, to include a slider, a transparent disk, means for directing a light beam directed between the slider and the disk, and means for iteratively measuring an estimated FH using at least two points of measurement on the slider when the slider is moved away from the disk at a pitch angle, wherein the estimated FH is computed as a function of the pitch angle and during each iteration, a previously-estimated FH is used to converge the estimated FH so that the estimated FH is within a predetermined range from the actual FH.