Methodology: How We Calculate

Official data verified · U.S. CPI-U · Annual average · NSA · Data through September 2026 (fetched 2026-11-02) · Series CUUR0000SA0

The data

All U.S. figures come from the Consumer Price Index published by the U.S. Bureau of Labor Statistics (BLS). The main series is CPI-U, all items, U.S. city average (series CUUR0000SA0), base period 1982-84=100. Alternative indexes offered on some calculators: core CPI (all items less food and energy, from 1957), CPI-W (urban wage earners) and the PCE price index published by the Bureau of Economic Analysis (from 1959 for monthly comparisons here). Average prices for gasoline and eggs are BLS average-price series. Data is republished from official releases; this site is not affiliated with BLS or BEA.

Not seasonally adjusted — on purpose

Every calculation uses not seasonally adjusted (NSA) index values. Seasonally adjusted figures are revised as new data arrives; NSA values are final when published. That is why NSA is the standard basis for contract escalation, lease adjustments and cost-of-living calculations — and why we use it everywhere, including where a headline news figure would use the adjusted series.

The formula

Adjusted amount = amount × (index at end ÷ index at start). Formula v1.0 — annual-average CPI, NSA (per-country basis on each methodology page).

• Year pages compare annual averages: the mean of a year's twelve monthly indexes. This matches the convention of the BLS inflation calculator for whole-year comparisons.
• Calculators can compare specific months; the result then uses those months' index values, and the page says so.
• Partial years: the current year's average covers only the months published so far and is labeled "partial". We never present a partial-year average as a full year, and we never insert forecast values into historical data.
• The missing month: BLS did not publish an October 2025 CPI (data collection was suspended during the federal government shutdown). The 2025 annual average therefore covers eleven months. We show the gap rather than estimating or interpolating a value.
• Two different percentages: the change in the price level and the change in purchasing power are not the same number. If prices rise 100%, purchasing power falls 50%. Pages state each figure under its own name.
• Deflation: for periods when prices fell (for example 1929–1933 or 2008–2009), pages show negative price change and rising purchasing power, computed with the same formula.

Revisions and corrections

NSA CPI values are not revised after publication. If another source series we display is ever revised, the change is recorded on the data updates page with the old and new values. If you believe a figure here is wrong, the verification panel on each page shows the exact index values used, and the underlying data can be checked in the BLS data finder.

Licensing

BLS and BEA data are U.S. government works in the public domain. Our calculations, text and presentation are our own.