Moment of inertia is very important when we design structural members.
An excellent online calculator is available which is very useful tool for mechanical, civil, and aeronautical engineers to determine moment of inertia (area moment of inertia) of plane sections.
It can be used to determine the centroid, area, moment of inertia, section modulus, radius of gyration etc. for rectangular, circular, T-section, I-section, Angle section, Channel section.
The calculator is available at the following link