[en] This paper describes the DENSI code in the FORTRAN langauge developed for calculation of nuclei quantity in targets according to the neutron transmission measured by the time-of-flight method and the preset values for isotope resonance parameters. The isotope quantities to be found are evaluated by approximation to the experimental dependence using the least square criteria of the transmission curve calculated by the Breit-Wigner one-level formula taking into account the Doppler-effect and neutron spectrometer resolution. The results on calculations of spectrum for osmium and uranium-plutonium oxide targets are presented as an illustration of the code validity