The present paper focuses on computational approach to analyze the heat loss due to natural convection and radiation in a trapezoidal shaped solar cooker. Heat losses due to forced convection and radiation are considered from the top glass cover. The results are verified with standard procedure. Radiative heat loss from the cavity is found to be dominant mode which contributes around 70–80% of the total heat loss. Parametric studies regarding heat loss from the cavity are studied by varying cavity depths, heat transfer coefficients based on the wind speed above the glass surface, emissivity of the plate. Based on different parameters, flow pattern and isotherms inside the cavity have been analyzed. Results are obtained in non-dimensional forms for more generic use and correlation between the total average Nusselt number and its influencing parameters has been formulated for the considered solar cooker cavity.