When you are looking to find your ROI or Return on Investment, you need to know first what an ROI is.  An ROI is a traditional financial way of measuring your investment return based on historic data.  It is simple way to figure out if your investment will have a positive or negative ROI or if there are other ways of bringing in a higher ROI.  It is just one of several approaches to building a solid financial case whether or not to make a financial decision based on comparing expected gains to the investment costs.