A simple procedure was devised for the preparation of a standard KCl powder to be used for the experimental determination of the instrumental profile in the Bragg–Brentano geometry. The standard was tested on several diffractometers, and narrow Bragg reflections in the range 28°–132° were recorded adopting various experimental conditions. Profiles were modeled with analytical functions, to describe the trend of width and shape of the instrumental profile as a function of the diffraction angle. Some indications were given to perform reliable profile fitting and line broadening analysis; a high resolution setup, obtained by employing narrow slits, large goniometer radius, and a monochromator in the diffracted beam, gives narrow reflections, even though the intensity of the diffracted beam is considerably reduced. The choice of these experimental conditions, which can be achieved using the majority of the commercial instruments, leads to symmetrical profiles, even at relatively low angle (2Θ=28°), which are highly recommended for reliable profile fitting and line broadening analysis.