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Macroeconomics

GDP Deflator Calculator

Derive the price index from nominal and real GDP and optionally compare it with the previous index.

User inputs or hypothetical examples · Consistent units and periods · Local calculation

Inputs

Amounts on this page use USD. Switching language uses that language’s own example or tab session; no currency conversion is performed.

Currently a hypothetical teaching example. GDP uses billion USD; keep periods and price bases consistent.

Results

Start with your numbers

Review or adjust your inputs, then calculate to see your results and interpretation.

Understand this calculation

An index of 120 is 1.2 times the reference price level. Against a previous index of 110, the two-period change is about 9.0909%.

See calculation method and assumptions

Formula

GDP Deflator

Current GDP deflator

Two-period implied price change

The implicit GDP deflator is same-period nominal GDP divided by real GDP, times 100. Its inflation rate is the percentage change between two index levels.

Variables, rates and periods

GDPnom
Current nominal GDP (billion TWD, at current prices)
GDPreal
Current real GDP (billion TWD, with a consistent reference basis)
D0
Previous GDP deflator (optional, index points)
D1
Current GDP deflator (index points)
πGDP
Price change calculated from the two deflator indices
Units
GDP uses billion TWD. D is in index points, with a reference price level of 100; π GDP is a decimal change, so 0.05 displays as 5%. Index points are not inflation percentages.

Before comparing two periods

  • Use the same period, unit and coverage for nominal and real GDP, and consistent index definitions and reference year across periods.
  • Follow the statistical publisher’s methodology for real data.
  • The interaction is a one-good price/quantity decomposition.

Derive the price index from nominal and real GDP and optionally compare it with the previous index.

Worked example

  1. Enter same-period nominal GDP 1,200 and real GDP 1,000.
  2. Use billion USD for both and a consistent reference-year price basis.
  3. The index is 120; compare with previous 110 rather than labeling 120 as an inflation percentage.

Frequently asked questions

Can I find inflation without a previous index?

You can calculate the current index only. The rate of change requires a previous index; a blank field never silently assumes 100.

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