Every month Doug Short at Advisor Perspective writes an excellent report on GDP. With today's release of the Q1 GDP Second Estimate, Doug Short has a new column worth a good look: Will the "Real" GDP Please Stand Up? (The Deflator Makes Big a Difference).
How do you get from Nominal GDP to Real GDP? You subtract inflation. The Bureau of Economic Analysis (BEA) uses its own GDP deflator for this purpose, which is somewhat different from the BEA's deflator for Personal Consumption Expenditures and quite a bit different from the better-known Bureau of Labor Statistics' inflation gauge, the Consumer Price Index.
The Lower the Deflator, the Higher the GDP
I have a note at the bottom showing the real GDP calculation method. Suffice to say that the higher the increase in compounded annual percentage change in the deflator, the lower the real GDP. Conversely the lower the increase (or if there is a decrease), the higher the real GDP.