The density is a geometric figure of the function of the coordinate ρ(x, y, z), so its total mass is: m=∫ρ(x, y, z)dxdydz,

The coordinates of the center of mass are:

xc=(∫xρ(x，y，z)dxdydz)/m

yc=(∫yρ(x，y，z)dxdydz)/m

zc=(∫zρ(x，y，z)dxdydz)/m

The above points are volume points.

If there are several particles, the center of mass can be calculated as follows:

xc =(m 1 * x 1+m2 * x2+m3 * x3)/(m 1+m2+m3)

YC =(m 1 * y 1+m2 * y2+m3 * y3)/(m 1+m2+m3)

ZC =(m 1 * z 1+m2 * z2+m3 * z3)/(m 1+m2+m3)