To calculate ROI, the benefit (or return) of an investment is divided by the cost of the investment, and the result is expressed as a percentage or a ratio. Capitalization Of Earnings · FYI On ROI: A Guide To · (SROI)?. It is expressed in percentage. It is found by dividing the net profit by the total assets. ROI is the ideal way to interpret and choose the best kind of investments. ROI calculations allows you to compare the results of different investments. ROI or Return on Investment calculates the percentage gained or lost on an.