The surface of a single crystal having etch steps of known heights can be used for magnification calibration. The etched basal surface of a hexagonal ferrite single crystal has etch steps whose heights are a precisely known function of its unit cell height. Depending upon the mixed‐layer stacking arrangement of the hexagonal ferrite phase such etch steps can have heights ranging in increments from 11.6 to 300 Å. After careful selection of a characterized hexagonal ferrite single crystal, it is etched in 1:1 HCl at 90°C until etch features are visible on the basal surface. The crystal is replicated by the one step method. The angle used for shadowing (from 1:1 to 3:1) must be accurately set since any error in the shadow angle will produce a corresponding error in the magnification. The shadow cast by the etch steps on the replica as viewed in the electron microscope is then used as the standard for calibration of magnifications in excess of 10 000 times.