GDP Deflator Formula Calculator

Enter nominal and real GDP for a current and a prior year to calculate the GDP deflator index for each and the resulting deflator-based inflation rate.

Quick Facts

Formula
Deflator = (Nominal GDP / Real GDP) × 100
Nominal GDP is valued at current prices; real GDP is the same output valued at fixed base-year prices.
Base year
Deflator = 100 by definition
In the base year, nominal and real GDP are equal, so the deflator always equals 100 there.
Inflation rate
% change in the deflator
(Deflator(t) − Deflator(t−1)) / Deflator(t−1) × 100 gives the deflator-based measure of inflation.

Your Results

Calculated
Current GDP deflator
-
Index, base year = 100
Prior-year GDP deflator
-
Same index basis
Inflation rate
-
Deflator-based, year over year
Price trend
-
Interpretation of the change

Ready

Enter nominal and real GDP for both years, then press Calculate.

How the GDP Deflator Calculator works

The GDP deflator is the broadest price index a national economy publishes: it measures how much the average price of everything produced domestically — consumer goods, business investment, government purchases, and net exports — has changed relative to a chosen base year. This calculator applies the standard textbook formula to nominal and real GDP figures for two years so you can see both the index level and the implied inflation rate.

The formula

For a given year, the GDP deflator is:

GDP Deflator = (Nominal GDP / Real GDP) × 100

Nominal GDP values total output at the prices that were actually charged that year. Real GDP values the same physical output using fixed prices from a base year, which strips out price changes and leaves only the change in quantity produced. Dividing the two isolates the pure price effect: in the base year nominal and real GDP are equal, so the deflator is exactly 100.

Turning the deflator into an inflation rate

Once you have a deflator for a current year and a prior year, the year-over-year inflation rate implied by GDP data is:

Inflation rate = (Deflator(current) − Deflator(prior)) / Deflator(prior) × 100

A positive result means the broad price level rose (inflation); a negative result means it fell (deflation). This calculator computes both deflators and this percentage change automatically from the four GDP figures you enter.

Worked example

Suppose current-year nominal GDP is $27,000 billion and current-year real GDP (in base-year prices) is $23,500 billion. The current deflator is 27,000 / 23,500 × 100 ≈ 114.89. If the prior year had nominal GDP of $25,500 billion and real GDP of $22,500 billion, its deflator is 25,500 / 22,500 × 100 ≈ 113.33. The implied inflation rate is (114.89 − 113.33) / 113.33 × 100 ≈ 1.4% for the year.

Key assumptions and limits

  • Same base year throughout: the real GDP figures for both years must be valued in the prices of the same base year, or the deflator and the inflation rate it implies will not be comparable.
  • Economy-wide, not consumer-only: the deflator reflects everything produced domestically, including investment goods, government services, and exports — not just what households buy, so it can diverge from the Consumer Price Index in a given year.
  • Provisional data: published GDP figures are frequently revised, and many statistical agencies use chain-weighting rather than a single fixed base year, which changes the deflator slightly from the simple fixed-base version calculated here.

Frequently Asked Questions

What is the GDP deflator?
The GDP deflator is a price index that measures the average change in prices of all goods and services produced in an economy, relative to a base year. It is calculated as Deflator = (Nominal GDP / Real GDP) x 100, and it equals 100 in the base year by definition.
How do you calculate the GDP deflator?
Divide nominal GDP (output valued at current-year prices) by real GDP (the same output valued at fixed base-year prices), then multiply by 100. A deflator of 112 means the overall price level is 12% higher than in the base year.
How is the inflation rate derived from the GDP deflator?
Compute the deflator for two periods, then take the percentage change: Inflation rate = (Deflator(current) - Deflator(prior)) / Deflator(prior) x 100. A positive result indicates rising prices (inflation); a negative result indicates falling prices (deflation).
How does the GDP deflator differ from the CPI?
The GDP deflator covers every good and service produced domestically - consumption, investment, government spending, and net exports - and its basket changes each period to match actual output. The Consumer Price Index tracks a fixed basket of goods bought by urban consumers, so the two indexes can move differently even in the same year.

Related calculators