Investing in projects nowadays presents great challenges and comes with a high dose of risk and uncertainty. Therefore, prior to investing in projects, detailed analyses need to be conducted to determine the degree of return on investment in the project. The most common method to evaluate the project's cost-effectiveness is the net present value of the project (NPV). The NPV depends on many input variables and if it is wrongly estimated, the investor can get a wrong picture of the project and expose himself to significant risks. For this reason, it is necessary to analyse how variations in input sizes can affect the cost-effectiveness of a project. For a successful assessment of the risk of the project it is of the utmost importance for the investor to correctly estimate variability of input variables (such as demand, prices of raw materials or energy, etc.). For this reason, it is necessary to analyse how variations in input sizes can affect the cost-effectiveness of a project. This final paper analyses the feasibility of building a poultry farm using the net present value (NPV) method, to test the sensitivity of the expressed NPV values to the input size variant. A sensitivity analysis is performed using senslt add-on for Excel. A risk analysis is performed by simulating input variables that are random (they are not subject of decisions made by the investor, but are a consequence of the environment) using Monte Carlo simulation software. This is @ Risk, which uses Excel as an interface. The main objective of the analysis is to identify which variables most affect the value of the NPV, and to determine the probabilities of possible adverse results that occurred in the event that a larger number of input variables had unexpectedly unfavourable values. Following the analyses, the NPV was found to be the most sensitive to the following input size as the observed cost-effectiveness measure: the price of chickens, the number of chickens and the rates of financing. The results of the analysis indicate that the project is very cost-effective, with the warning that additional actions need to be carried out to protect the business from risk.