GDP Deflator Calculator
Calculate the GDP deflator from nominal and real GDP, convert nominal GDP to real (or back), and get the inflation rate between two periods.
The GDP deflator measures how much of the change in GDP comes from prices rather than output. It compares GDP at today's prices (nominal) with GDP at base-year prices (real). Economics students use it to convert between nominal and real figures, and analysts use it as a broad inflation gauge that covers everything an economy produces, not just a consumer basket.
How to use this tool
- Pick what you want to find: the deflator, real GDP or nominal GDP.
- Enter the two figures you know, in the same units.
- Optionally add the previous period's deflator to get the inflation rate.
- Read the result and the price change since the base year.
Formula
GDP deflator = nominal GDP ÷ real GDP × 100
Real GDP = nominal GDP ÷ (deflator ÷ 100)
Inflation = (deflator now ÷ deflator before − 1) × 100
In the base year nominal and real GDP are equal, so the deflator is exactly 100. A value of 121.7 means the general price level of domestic output is 21.7% above the base year.
Example
An economy with nominal GDP of 28,000 and real GDP of 23,000 (both in billions) has a deflator of 28,000 ÷ 23,000 × 100 = 121.739. Prices are 21.74% above the base year, and the nominal-minus-real gap is 17.9% of nominal GDP. That reference-year-dependent gap is not a decomposition of GDP growth. If last year's deflator was 118, inflation was 121.739 ÷ 118 − 1 = 3.169%.
Frequently asked questions
How is the GDP deflator different from the CPI?
The CPI tracks a consumer basket with periodically updated weights of goods consumers buy, including imports. The deflator covers all domestically produced goods and services — investment and government spending too — and its weights change as the economy changes.
Where do I get official figures?
In the United States the Bureau of Economic Analysis publishes nominal GDP, real GDP in chained dollars and the GDP price index each quarter. Other countries' statistics offices publish the same series.
Can the deflator fall below 100?
Yes — for years before the base year, or after a period of deflation, prices are lower than in the base year and the index is below 100.
Sources
Last updated: 2026-10-30