Below you can download an Excel worksheet that will help you calculate the cost of your capital. Your cost of capital is important to know for several reasons. Mostly, it gives your board and shareholders a yardstick in which to gauge a bank’s return. Produce over your cost of capital and you will be able to attract more capital. Produce under and, well, you are going to have to do some good marketing to talk investors into believing you are better than the next similar investment alternative.