An analytical approach is presented for determining the characteristics of the zones of a planar kinoform lens of any specific order for stigmatic imaging between extra-axial conjugate points. It is shown that, by use of a suitable normalization, the zone characteristics are obtained in terms of dimensionless variables. This facilitates ready estimation or comparison of pertinent zone parameters in given applications. The convenient amenability of the approach to the case of reflective kinoform lenses is also indicated.