RealWorth

Methodology

How we calculate inflation and purchasing power

CPI-Based Conversion

Our core calculation uses the Consumer Price Index (CPI) ratio method:

Adjusted Amount = Original Amount × (CPI_toYear / CPI_fromYear)

This method is the standard approach used by central banks and statistical agencies worldwide. It answers: "How much money would you need today to have the same purchasing power as X in year Y?"

Year Interpolation

When a specific year does not have a CPI data point (common for pre-1913 data), we use linear interpolation between the nearest available data points. Interpolated results are flagged in the underlying calculation objects. For gaps greater than 10 years, results carry wider uncertainty.

Pre-1913 Data (USA)

Official BLS CPI data begins in 1913. For earlier years, we use the Warren & Pearson Wholesale Price Index, rescaled by Officer & Williamson via MeasuringWorth.com to be consistent with the modern CPI-U series. This is the same approach used by academic economists and is regarded as the best available reconstruction. The Civil War inflation spike (1861–1865) and subsequent Gilded Age deflation are reflected.

Pre-1914 Data (UK)

For pre-1914 UK data, we use the Bank of England "Millennium of Macroeconomic Data" dataset (Broadberry, Campbell, Klein, Overton, van Leeuwen, 2015), supplemented by Clark (2005) "The condition of the working class in England, 1209–2004." This covers Napoleonic War inflation (1800–1815) and the long Victorian deflation through 1896.

Roman Empire

Roman data uses a commodity basket purchasing power parity (PPP) approach, primarily anchored on wheat prices (a universal staple). The methodology:

  1. Establish wheat price in sesterces per modius from surviving papyri (Temin, 2001)
  2. Calculate modern USD equivalent of one modius of wheat (~$8 in 2024)
  3. Derive a PPP conversion factor from this commodity anchor
  4. Apply the same factor to wage and other price data
⚠ Roman Empire values carry very high uncertainty. Treat all figures as order-of-magnitude estimates only.

Limitations

  • CPI measures average consumer prices; it may not reflect your personal spending basket
  • Different economists use different methods (GDP deflator, PCE index, etc.) — results vary by method
  • Pre-industrial economies had different consumption patterns; comparisons across centuries are inherently approximate
  • Wage data represents national averages; regional and occupational variation can be substantial
  • 2025–2026 values include projected/preliminary data and may be revised