The expenditure method is the most widely used approach for estimating GDP. GDP is calculated by summing expenditures on final goods and services, including: 1) Consumer spending (C) 2) Government spending (G) 3) Business investment (I) 4) Net exports (Exports - Imports) (NX) Using this formula: GDP = C + G + I + NX Several expenditures are excluded from this calculation, such as purchases of used goods, financial assets, and transfers. The document provides examples of calculating GDP using expenditure data.