I have a disk with some thickness to it and I need its moment of inertia. So this is the formula with r1=0 Now there is a "circular hole of diameter 'd' at a distance of 'r' from the geometric center of the disk." So I'm thinking that I should subtract the MoI of the hole from the disk. Here is a picture if you need it. http://img99.imageshack.us/img99/782/50817033.jpg [Broken] I could use the same MoI equation as I did for the disk on the hole but that doesn't account for the hole being off centered. Any ideas?? I need to eventually equate this to a small mass rotating around a center point, so if there is a more direct approach please tell me. Thanks in advance for the help.