Economies of scale are one of the important behavioral indicators of production units. In the presence of economies of scale, the scale curve is descending, which indicates a decrease in the average cost of production with an increase in production. Theoretically, the optimal size of a production unit is the volume of production at which the average cost is at its lowest. The issue of the need to pay attention to economies of scale and optimal allocation of resources on the one hand and the role and position of hospitals in providing medical services on the other hand and the high share of treatment costs in public spending in Iran, compared to the world average, The motivation was to evaluate the efficiency conditions in production and determine the optimal size of the hospital. In this study, in order to determine the optimal size of Shahid Rahnemoun Hospital in Yazd according to the number of beds, the cost quadratic function of the hospital translog was estimated based on production factors using the quadratic cost function method. The study period is 1390-1398, which uses Eviews econometric software.