The main objective of this study is to show a method for calculating entropy generation (Sgen) in a human body under various environmental and physiological conditions. The Sgen in a human body is a measure of activeness of motions, reactions, and irreversibility of processes occurring in a body and is a kind of holistic and thermodynamic index, which characterizes a human body as a whole. Human body at healthier and normal condition generates the least amount of Sgen. Heat transfer over a human body, activity (at rest, Sgen = 0.21J/sK or exercise, Sgen=2.19 J/sK or at death, Sgen = 0J/sK), ambient, body and mean radiant temperatures, emissivity and absorbity of human skin, internal heat elimination, body weight and height, and air speed effect much more on the Sgen in a human body compared to the effects of mass exchange into and out of the body, internal heat production, cross-sectional area of human body, clothing, altitude, and relative humidity of the surrounding air. Among these factors entropy production due to heat transfer over a human body plays a significant role in the total entropy generation rate. .