Identify the time period and geographic area
Choose the GDP method: expenditure, income, or production
Expenditure method: add consumption, investment, government spending, and net exports
Use the formula GDP = C + I + G + (X – M)
Consumption includes household spending on goods and services
Investment includes business spending, residential construction, and inventory changes
Government spending includes public purchases of goods and services
Net exports equal exports minus imports
Income method: add wages, rent, interest, and profits
Production method: add value added at each stage of production
Use nominal GDP for current prices
Use real GDP for inflation-adjusted prices
Apply a GDP deflator or price index to adjust for inflation
Sum all final goods and services only
Avoid double counting intermediate goods
Compare the result with official statistical data if needed