In this paper, the aim is obtaining convection coefficient of human body. At first a 3D human body has been designed by unstructured grids. Feet and hands are stretched completely in considered sample. Two segments (standing and supine) are considered for body. Soles and the back of entire body are considered in contact with the ground respectively in these segments. Other parts of human body are exposed to surrounding air. The heat transfer and the body temperature are assumed steady and constant. The results are obtained by applying finite volume method for each grid and extracted by the weighted area method. Then the attained results are validated with the recent experimental results. Good agreement is observed between the obtained results and the previous experimental results. Finally two formulas are derived for natural convection coefficient of human body.