the ROI metric allows an investor to quantify the success of an investment. A reliable figure can be calculated after the investor has sold their investment, but ROI is used extensively as an estimated forecast based on plans and expectations. ROI is usually expressed as a percentage increase in the value of an investment per year, or over the lifetime of the investment. Inside companies, projects and initiatives are often judged as investments with ROI. But in this case, cost savings and revenue growth are the main return.