The ROI calculator can be used to evaluate the efficiency of an investment or to compare the efficiency of a number of different investments. To calculate ROI, the benefit (return) of an investment is divided by the cost of the investment; the result is expressed as a percentage or a ratio.

Return on investment is a very popular metric because of its versatility and simplicity. If an investment does not have a positive ROI, or if there are other opportunities with a higher ROI, then the investment should be not be undertaken.