A program of transformer cooling system calculation aimed to define temperature rise of top oil layers in the tank above ambient air temperature, and average temperature rise of oil in the cooling system. The software allows performing calculations of the radial cooling systems and installed air or water coolers as well with the bottom or side fans location with availability or absence of oil pumps. Thetaskperformanceisbasedontwodifferentapproaches. The first one is based on the experiments planning method where availability of the results of similar cooling system is obligatory. Thesecondisbasedonjoint solution of the heat balance and heat transfer equations. Heattransferfactorsfortheheat transfer equation are defined by the Similarity Theory criteria equations with Grashoh, Reinolds, Prandtl and Nusselt numbers usage.