The possibility of taking account of the granulometric composition of coke in assessing its metallurgical properties is considered. In practice, the main coke characteristics vary with forced or deliberate change in the coal batch. The research is based on operational data for blast furnaces and the characteristics of coke in periods when its hot strength and granulometric composition change. A priori data regarding the influence of the hot strength CSR on the decrease in piece size of the coke in the reaction zone are used to formulate an equation taking account of both the equivalent diameter of the coke pieces and their CSR values. The proposed index takes better account of the change in blast-furnace operating conditions with change in coke quality.