Gross Domestic Product (GDP) is one of the most important indicators used in project analysis and economic planning to measure the economic performance of a country. It represents the total monetary value of all final goods and services produced within the domestic territory of a nation during a specific period, usually a year or a quarter. In project analysis, GDP estimation helps in understanding the macroeconomic environment, assessing market potential, evaluating investment opportunities, and forecasting future growth trends that influence project viability and sustainability. The estimation of GDP can be carried out through three main approaches, namely the production or value-added method, the income method, and the expenditure method. Each approach measures GDP from a different perspective but theoretically yields the same result because total production equals total income and total expenditure in an economy. The production or value-added method calculates GDP by summing the value added at each stage of production across all sectors of the economy, such as agriculture, industry, and services. Value added is obtained by subtracting the cost of intermediate goods from the value of output produced by each enterprise. This method avoids the problem of double counting because only the net contribution at each stage is considered. In project analysis, this method is useful in sectoral studies where analysts evaluate how a project contributes to overall economic output by generating additional production in a particular industry. The income method estimates GDP by adding all incomes earned by factors of production in the economy, including wages and salaries, rent, interest,