The computer program SOLANG, originally developed by MOENS et al. for the efficiency conversion via effective solid angles (Ω), is extended in this work to cylindrical sources with a diameter larger than that of the Ge-detector. New program, named EXTSANGLE, is experimentally checked in our three laboratories. For the most unfavourable case from the standpoint of the accuracy of\(\bar \Omega \) (bulky source counted at the top of detector), discrepancies were below 7% in the whole range of gamma-energies considered (88–1115 keV), with an average of 3–4%. EXTSANGLE is extensive and flexible with respect to the data input, storage and output, thus contributing to the automation of a gamma-spectrometry laboratory dealing, for instance, with the k0-NAA and/or environmental radioactivity monitoring.