Blood transfusion services are an important part of modern medical services that use human blood as a basic material with humanitarian purposes and not for commercial purposes (Article 86 of Law Number 36 of 2009 concerning Health and in accordance with PP No.7 of 2011 concerning Services Blood Descriptive Method, retrospective, cross-sectional study, transfusion blood requested by the clinician for patients admitted to the hospital during the period of January 2016 to December 2017. Data on blood demand from the Hospital with criteria for age, sex, number of blood crossmatch requests and Crossmatch Transfusion Ratio (C / T ratio), Transfusion Index (TI) and Transfusion Probability (T%) were calculated, Results of 189,751 blood requests at the Surakarta Red Cross City Blood Donation Unit in Surakarta City and crossmatching tests totaling 188,581 bags blood with the amount of blood transfused The 187,620 bags calculated by C / T ratio are 1.005, TI is 0.995% and T% 0, 988%.

Keywords : C / T Ratio, Transfusion Probability, Transfusion Index.