Theorem of Parallel Axis

Theorem of parallel axis states that if the moment of inertia of a plane area about an axis in the plane of the area through centroid be represented by I_G, then the moment of inertia of the plane about a parallel axis AB (I_AB) in the plane at a distance h from the centroid of the area is given by (Figure 11.16)

Figure 11.16 Parallel Axis Theorem

I_AB = I_G + Ah²