GDP Deflator Calculator (nominal ÷ real GDP × 100, with inflation)

Understanding the GDP deflator calculator — concept and principle

This calculator finds the GDP deflator, the broad price index of everything produced in an economy, from nominal and real GDP. It also shows the price level change since the base year, inflation since the previous year and the price effect in money. Use it for macroeconomics homework, converting between nominal and real GDP and comparing the deflator with consumer price inflation.

The part of nominal GDP not explained by real output is the price effect; the ratio gives the deflator 120.

How it is calculated

GDP deflator = nominal GDP ÷ real GDP × 100.
Price change since the base year = deflator − 100 (%).
Inflation since the previous year = (deflator this year ÷ deflator last year − 1) × 100.
Price effect = nominal GDP − real GDP.

The principle

Nominal GDP values output at current prices; real GDP values the same output at base-year (or chained) prices. The ratio between them isolates the effect of price changes. In the base year the deflator is 100. Unlike a consumer price index, the deflator covers everything produced at home, including investment goods and government purchases, and excludes imports, and its basket changes automatically with what the economy produces.

Worked example

Default inputs: nominal GDP 24,000, real GDP 20,000, previous deflator 116.5.

Deflator = 24,000 ÷ 20,000 × 100 = 120.
Prices are 20% higher than in the base year.
Inflation since the previous year = 120 ÷ 116.5 − 1 ≈ 3%.
Price effect = 24,000 − 20,000 = 4,000.

Each point is the calculator re-run with only “Real GDP (base-year or chained prices)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Real GDP (base-year or chained prices)	GDP deflator
5,000	480
10,000	240
15,000	160
20,000	120
25,000	96
30,000	80
40,000	60

How to read the result

A deflator of 120 means the general price level of domestic output is 20% above the base year. Year-to-year changes give a broad measure of inflation. It can differ from CPI inflation because import prices, such as oil for a country that imports it, affect CPI but not the deflator, while investment-goods prices affect the deflator but not CPI.

Common mistakes

Swapping nominal and real GDP.
Comparing deflators with different base years.
Treating the deflator as a measure of the cost of living.
Forgetting to multiply by 100.

Keep in mind: Official deflators come from national statistics agencies and are revised as data improve. This is not financial advice.

Frequently asked questions

What is the difference between the GDP deflator and CPI?

The deflator covers all domestic production; CPI covers a fixed basket of consumer goods, including imports.

How do I convert nominal GDP to real GDP?

Real GDP = nominal GDP ÷ deflator × 100.

Why is the deflator 100 in the base year?

In the base year nominal and real GDP are valued at the same prices.

Sources: U.S. Bureau of Economic Analysis, Glossary: "Implicit price deflator (IPD)"

Checked 9 Nov 2026. U.S. Bureau of Economic Analysis, Glossary: “Implicit price deflator (IPD)” — the ratio of the current-dollar value of a series such as GDP to its chained-dollar value, multiplied by 100.

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