It is very difficult to get the amount of confidence or certainty factor (CF) patients to gelala experienced. In this study, the researchers propose a method of calculation of the amount of CF users on the system application specialist for the diagnosis of disease by using the quantification of questions methods. By using this method, experts expected the system will become easier to use because patients do not need to take into account the amount of CF symptoms experienced, but simply enter the quantity and duration of the symptoms experienced. The system will automatically calculate the value of CF users. CF value obtained by seeking membership function of quantity and duration of the patients included in the value of the rules given by the experts. This methods have been implemented in the specialist system to handle disease by using the Delphi programming language and database box.