← Economics Explained · Learning path

What is GDP and how is it calculated?

Gross domestic product measures production within an economy over a period. The expenditure identity is GDP = C + I + G + X minus M: household consumption, investment, government purchases, exports and imports. Investment here means produced assets and inventory accumulation, not purchases of existing shares. Transfers are not government purchases of current output. Imports are subtracted to remove foreign production already counted in spending components. The subtraction does not establish that imports are economically harmful.

Three lenses on the same activity

Production accounts add value created at each stage. Expenditure accounts track final uses. Income accounts track income generated in production. Consider wheat sold for 30, flour for 50 and bread for 100. If these are the only stages and inputs, value added is 30 + 20 + 50 = 100, not 180. Official accounts are more complex and may include statistical discrepancies.

Nominal, real and per person

Nominal GDP uses current prices. Real GDP adjusts for price changes to examine volume. GDP per capita divides GDP by population. It is an average, not median household income. A country can have positive total real growth and declining real output per person. Purchasing power parity measures help compare output or consumption volumes across countries, but they are not market exchange rates for settling foreign debts.

Illustrative growth calculation

If a real output index rises from 200 to 206, growth is (206 / 200 minus 1) × 100 = 3%. If population rises 1%, output per person grows by 1.03 / 1.01 minus 1, approximately 1.98%. If nominal output grows 7% while its appropriate price deflator grows 4%, real growth is approximately 1.07 / 1.04 minus 1 = 2.88%. Do not automatically use consumer inflation to deflate GDP.

Read the quality of growth

Identify which components contribute, whether inventories or temporary factors dominate and whether household income and investment support the trend. Productivity is output relative to an input, such as output per hour. It differs from simply working more hours. Long term living standards depend on productive capacity and its distribution. GDP does not fully summarize inequality, unpaid care, environmental damage or wellbeing.

Before comparing countries

Match the price basis, currency, reference period and annualization. Use published contribution tables for chain linked GDP rather than assuming chained component values add exactly. Separate a larger economy from a faster growing economy and from a richer population.

Sources and further reading

Examples use hypothetical figures unless stated otherwise. Updated 8 October 2026.