Gamma heating, which is deposited in irradiated targets or samples, is an important issue in research reac-tors because it affects the safety of samples and the reactor operation. Gamma heating in the Reaktor Serba Guna G.A. Siwabessy (RSG GAS) can be measured or calculated using computer code. In this paper, we present the results obtained by using gamma calorimeters to measure the gamma heating in the central irradiation position in RSG GAS. The measurement results were verified and then compared with the calculation results obtained using the Gamset code. However, the accuracy of the calculation results obtained using Gamset was inadequate, with more than 20％error. Moreover, Gamset was initially created to calculate gamma heating in 35 MWth reactors, and the RSG GAS reactor has an operating power level of 30 MWth. To address these issues, we developed a new pro-gram called NewGamset, built with an informative graphical user interface-based display. NewGamset can employ new analytical approaches as it utilizes a calcula-tion base that comprises 18 energy groups and can provide updated physical parameters of RSG GAS. The results of gamma heating measurements obtained using gamma calorimeters made of graphite, aluminum, iron, and zirco-nium were 2.20 ± 0.03 W/g, 2.25 ± 0.02 W/g, 2.58 ± 0.03 W/g, and 2.91 ± 0.10 W/g, respectively. In general, the calculation results were larger than the mea-surement results, and the average ratio of calculation to measurement result was 1.37 for Gamset and 1.02 for NewGamset. Hence, it can be concluded that NewGamset provides more accurate results than Gamset. We also report the gamma heating estimation for common elements irra-diated in the RSG GAS silicide core, with an operating power level of 15 MWth and 30 MWth. We highly rec-ommend that NewGamset be used for validating the gamma heating data of various target materials in RSG GAS.