By applying Stokes' Fourier transform method for the analysis of diffraction maxima it is shown that the pure diffraction contour generated by a crystallite size distribution is apt to be approximated rather closely by the function 1/(1+k2&phgr;2). In the case of the x‐ray spectrometer this pure diffraction contour is broadened significantly by the action of the following five geometrical factors: (I) the x‐ray source width, (II) flat rather than curved sample surface, (III) vertical divergence of the x‐ray beam, (IV) penetration of the sample by the beam, and (V) the receiving slit width.The broadening of the pure diffraction contour due to the action of each of the five factors and the breadth of the final contour generated by the instrument can be deduced by employing the convolution approach suggested by Spencer. The effect of each instrumental factor is expressed by a convolution equation of the formfi(&phgr;)=−∞+∞Wi(&zgr;)fi−1(&phgr;−&zgr;)d&zgr;,in which &phgr; is the angular displacement from twice the ideal Bragg angle, 2&thgr;,fi−1is the contour before the action of theith geometrical factor,Wiis the form of theith geometrical factor, andfiis the contour after the action ofWionfi−1. Starting with a pure diffraction contour of the form 1/(1+k2&phgr;2), generalized broadening curves are derived for the effect of each of the five geometrical factors. Using these curves it is possible to predict the breadth of the final diffraction contour generated by the spectrometer from an initial contour of any breadth.