Performance measure used to evaluate the efficiency of an investment and to compare the efficiency 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 common metric because of its versatility and simplicity. That is, if an investment does not have a positive ROI, or if there are other opportunities with a higher ROI, then the investment may not be undertaken.