Methodology

This site estimates inflation-driven purchasing power changes using consumer price index (CPI) ratios. It’s a lightweight, static calculator intended for clear comparisons between years, not a personalized cost-of-living forecast.

What “equivalent amount” means here

For a chosen amount and year range, we compute an inflation-adjusted “equivalent amount” based on the CPI ratio between the start year and end year. Conceptually, this is the end-year amount that would have similar purchasing power to the start-year amount, in the same currency.

The formula

Using CPI index values from /data/cpi and the definitions in docs/DATA_MODEL.md:

Equivalent amount = A × (CPI_end / CPI_start)
Inflation shortfall = equivalent amount − A
Shortfall percent = (inflation shortfall / equivalent amount) × 100
Inflation factor = CPI_end / CPI_start

How to use the results

Step 1

Choose a range

Pick two years that exist in the country’s CPI series.

Step 2

Compare purchasing power

The equivalent amount reflects end-year prices in the same currency.

Step 3

Interpret the shortfall

Use shortfall and factor to compare how prices changed over time.

Validation rules

Amount must be greater than 0
Start year must be earlier than end year
Both years must exist in the selected country’s CPI series

Limitations

CPI is an average index. Inflation varies across categories (housing, energy, food, services) and across regions, so your personal experience may differ. Different CPI sources and rebasing choices can also lead to slightly different results.

Next step

Use the inflation loss calculator to explore scenarios, then visit a country page to see CPI coverage, sources, and popular prefilled links.

Methodology FAQTap to expand

Methodology FAQ

Answers to common questions about CPI-based inflation loss estimates.

Why use CPI ratios instead of inflation rates?

CPI ratios are the direct way to convert a start-year amount into end-year prices using the CPI index values.

Does the calculator include taxes or wages?

No. It strictly adjusts the nominal amount by CPI; it does not model income or tax effects.

Why do results differ from official calculators?

Different CPI series, rebasing choices, and rounding conventions can produce slightly different outputs.