The center of mass of a person standing upright is located near a point between the hips. By lifting one leg or one arm, the center of mass is raised by only 1 or 2 cm because the mass of one arm or one leg is only a small fraction of the total body mass. Consequently, we can usually visually estimate the position of the center of mass to within 1 or 2 cm. Otherwise, the position of the center of mass of each body segment needs to be estimated, in which case the (x, y) coordinates of the center of mass of the whole body can be found as a weighted means.