The general definition for the angular momentum, L, of a point mass about a reference point is given by

    L = r x p

where r is the vector from the reference point to the mass and p is the linear momemtum of the point mass.

For the special case of rotation of a rigid body about a fixed axis, with the axis of rotation taken to be in the z direction, the magnitude of the angular momentum, L, and the z component of the angular momentum, L_z, are given by

    L = I*w

    L_z = I*w_z

where I is the moment of inertia of the rigid body about the given axis of rotation and w is the angular velocity of that body.