Conic mirror reflectometers are used to measure the diffuse reflectance and total integrated scatter of surfaces. In spite of the long history of using conic mirrors for these purposes, the maximum magnification of the three primary types of conic mirrors [hemisphere, hemi-ellipsoid, & dual-paraboloid] has not been previously compared quantitatively. In fact, only for the hemi-ellipsoid has an exact formulation of the magnification been published. The maximum magnification is needed to properly size detectors and radiation sources used with reflectometers. In this paper, exact analytic expressions for the maximum magnification of both a Coblentz hemisphere and a dual paraboloid mirror system are derived and compared with the well-known expression for a hemi-ellipsoidal mirror.