<p>National metrology institutes (NMIs) and Designated Institutes (DIs) play a crucial role in establishing and maintaining measurement standards within a country. These institutes are responsible for ensuring the accuracy and traceability of measurements across various fields, including radiation metrology. In India, Radiation Standards Section (RSS) of Bhabha Atomic Research Center (BARC) is the DI and is responsible to develop, establish and disseminate the ionizing radiation standards. As the measurement of activity using primary standards is destructive, cumbersome and time consuming, secondary standards are used to conserve the unit of activity realized by primary standards. The secondary standards are fast and non-destructive and routinely used for activity measurements provides results with slightly higher uncertainty. The 4π Gamma Ion Chamber (GIC) is used as a secondary standard at RSS for activity measurements of gamma emitting radionuclides. The activity of the sample of a gamma emitting radionuclide was determined by measuring the current produced in the GIC using the sensitivity coefficient of a particular radionuclide in the given geometry. Overall, uncertainty evaluation is an essential part of the measurement process ensuring the reliability and traceability of activity measurements carried out using gamma ion chambers. By quantifying and reporting uncertainties, demonstrates the quality and comparability of activity measurements. Various quantities contributing to the overall uncertainty in measurement of activity is described in the paper. The method of the evaluation of uncertainties in these quantities is also discussed in detail.</p>