In gamma ray spectrometry, a rigorous determination of radionuclide concentration for voluminous samples depends mostly on the proper efficiency calibration. The detection efficiency may differ due to sample density, sample measurement geometry, self–absorption and detection system, etc. The aim of this work to evaluate how the efficiencies are varied in different measurement regimes for environmental samples. The efficiency calibration was observed in gamma measurement system (HPGe detectors) with the relative efficiency of 40%. Environmental samples with the density ranging from 0.55 to 1.59 g/cm3 in 240 cm3 cylindrical containers were used for efficiency calibration having gamma energy 121 KeV to 1409 KeV. All the secondary reference materials were made by using Eu-152 standard liquid source. The variation of efficiency was found from 63.2% to 76.8% due to the difference in sample matrix and variation due sample position from detector surface was 6% to 40%. Whilst due to variation in sample weight the calculated efficiency values were ranging from 27% to 60%. The evaluated result will be useful to calculate the accurate radionuclide concentration in environmental sample.