ES70 Moments About a Point 

The moment about a point is defined as shown here
where
 unit vector perpendicular to
(the position vector) and
(the force) following the right hand rule.

The geometric configuration is demonstrated here. 
where M = (r_{y}·F_{z}  r_{z}·F_{y})i  (r_{x}·F_{z}  r_{z}·F_{x})j + (r_{x}·F_{y}  r_{y}·F_{x})k 
The moment may be given in component form as shown
where r_{x}, r_{y} and r_{z} are the component of the position vector r and
F_{x}, F_{y} and F_{z}
are the components of the force vector F.


For example, if is applied at the location specified by as specified here... 

... then the moment can be calculated as shown here. 