A correct cold room heat load calculation ensures that the refrigeration system operates efficiently, reducing operating costs while maintaining a constant temperature to prevent stored goods from spoiling. Refrigeration engineers typically use software to size equipment such as expansion devices and evaporators and to estimate heat loads in cold rooms. These tools are available for free from refrigeration manufacturers or can be purchased from software developers. Although practical and easy to use, most of these programs do not follow the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)-recommended approach for estimating heat loads. This article evaluates heat transfer mechanisms, especially natural convection in a refrigerator, through experimental and CFD simulations. Depending on the expression used, the estimated convection heat flux at the evaporator ranged from 5.3 W to 14.2 W in case 0-N, 7.7 W to 25.1 W in case -10-N, and 5.1 W to 22.4 W in case 0-Y. Compared to convective heat transfer, radiation heat flux estimations are often more consistent across different expressions. The results from validated simulations were used to assess the performance of cold room heat load estimation software. Differences of up to 236% in heat load estimates were reported between the results.