## Calculating the radius of gyration

To calculate the radius of gyration for the cross-section of the beam in the diagram, start with the values of **I** that were calculated earlier.

I_{xx} = 33.3 x 10^{6} mm^{4}

I_{yy }= 2.08 x 10^{6} mm^{4}

Refer to the diagram for the values of b and d that are used in the calculation of A.

A = Area of cross-section = 50 mm x 200 mm = 10,000 mm^{2}

Substitute **I** and A into the formula for **r** to give:

This is the value of the radius of gyration about the x-x axis.