Hi,

The moment of inertia of a body about an axis is sometimes represented using the radius of gyration. We can define the radius of gyration as the imaginary distance from the centroid at which the area of cross-section is imagined to be focused at a point in order to obtain the same moment of inertia. It is denoted by k.

Its formula is like : k = √ ( I/m )

where I is the moment of inertia of that body and m is the mass of that body.

Hope it helps.