In finance, return on investment (ROI), also called rate of return (ROR), profit rate, or simply return, is the ratio between the amount of money gained (or lost) as a result of an investment and the amount of money invested. There are three possible formulations of rate of return: effective return; required return; and projected return. The effective return serves as a measure of the performance of an investment, assessed a posteriori. The projected return serves as an ex ante measure of the performance of an investment; it is its implicit or internal rate of return, the one that equates the value of the investment to its price or cost. The required rate of return is what allows us to determine the value of an investment. In fact, the value of an investment is the present equivalent of its future cash flows, these being converted into present equivalent (or discounted) precisely at the required rate of return. It is based on the idea that any investment should provide a rate of return equal to a risk-free rate plus a risk premium that is a function of the degree of uncertainty affecting the investment's future cash flows. The expected rate of return is a function of the price (or cost) of the investment and the flow of future cash flows attributable to the investment. Since these cash flows are uncertain, the expected rate of return is also uncertain, even appearing as a random variable. This is where its risk lies, which must be measured to be taken into account in estimating the risk premiums to be included in the required rates of return. The amount of money gained or lost can be referred to as interest, profits or losses, gains or losses, or net income or net losses. The money invested can be referred to as assets, capital, principal, or basic cost of the investment. ROI is generally expressed as a percentage. The realization of a company's organizational strategies depends on the proper management of projects, programs, and portfolios. In this sense, financial responsibility is constantly increasing, and its measurement is mandatory. Although today the use of this analytical tool is widespread across all types of investments, calculating ROI is not a recent "trend." As early as 1920, the Harvard Business Review referred to ROI as the essential analytical measure for understanding the value of capital investment returns. Knowing this in advance has a significant impact not only within the organization managing the investment process, but also on potential investors. Beyond internal and external "selling" of the project, it is fundamental for its monitoring, clearly showing the impact on the business against pre-defined goals.