Return on investment (ROI) is a performance measure used to evaluate the efficiency or profitability of an investment or purchase, or compare the efficiency of a number of different investments or purchases. ROI tries to directly measure the amount of return on a particular investment, relative to the investment’s cost. To calculate ROI, the benefit (or return) of an investment is divided by the cost of the investment. The result is expressed as a percentage or a ratio. For purposes of calculating ROI on a sales or marketing investment, the “return” should be the resulting Gross Margin generated as a result of the investment, not the revenue.