The full-energy peak (photopeak) efficiency and peak-to-total ratio of a closed-end coaxial high-purity germanium detector were calculated and compared with the experimental measurements in the energy range between 60 and 1863 keV. The attenuation of photons by the source itself (self-absorption), the source container, and the detector end cap materials is also included. Many experimental readings have been taken for the source-detector system used in this investigation. By comparison, the calculated and experimental full-energy peak efficiency and peak-to-total ratio values are in good agreement; the overall percentage error is <3%.