A method based on zero, first, and second moments of the radiographic image density profile for the extraction of dimensions is presented. The method relies on knowledge of the ideal profile of the examined item, while the detailed shape of the line spread function (LSF) is not essential. The moments method was applied to determine the dimensions in a calibrated nuclear fuel pin examined by neutron radiography. Widths of pellet-to-pellet gaps and the diameter of the pin were determined and compared with the nominal values. The method is most suitable for dimensions smaller than the LSF width. The derivative method is shown to be completely in error, especially for the small pellet-to-pellet gaps. The study suggests an experimental method for measuring the second central moment of the LSF.