Large metros (Size A): inflation calculator and CPI-U since 1986

What "Size Class A" means

The BLS sorts every sampled area into one of two population-size classes. Areas above 2.5 million people are "self-representing": in the words of the BLS Handbook, "their weight in the CPI corresponds to their population relative to the U.S. population" (BLS Handbook, design). Areas below that size "represent not only themselves, but other areas in their region and size class", and they make up Size Class B/C. Size Class A is the index of the first group, combined across the country. The 2018 sample has 21 such areas above 2.5 million, plus Anchorage and Honolulu, which are also self-representing because their markets are isolated. Together the 23 self-representing areas hold about 42 percent of the CPI-U population, according to the Handbook.

When Size A is the right index

Most people with a big-city amount should use the metro itself: the CPI by city page lists all 23. Size A fits other cases. A contract that covers staff or sites in several large metros can name one index instead of five. A study of whether big cities inflate faster than small ones needs Size A against Size Class B/C. And Size A is monthly, while only New York, Chicago, Los Angeles among the metros are priced every month, so it gives a value for every anniversary date. The BLS urges users "to consider adopting the national or regional CPIs for use in escalator clauses"; Size A is a national index for one class of areas, and the final choice is the user's.

Big metros against the rest, by group

Over the latest 12 months, Size A shelter moved +3.0 % against +3.4 % in Size B/C. Energy was +19.5 % against +21.1 %. Medical care ran slower in big metros (+0.9 % against +2.0 %). Group series for Size A start in January 1997.

The record since 1988

The first annual change on this index is for 1988. Its fastest year since then is 2022, at 7.8 %; its slowest is 2009, at -0.3 %. A Size A amount from 1987 has grown at 2.85 % a year, faster than the 2.81 % of the U.S. city average over the same span.

The base and October 2025

Because the base is December 1986, the Size A level for September 2026 is 309.738, while the U.S. city average on 1982-84 stands at 336.94: never mix the two in one ratio. Like every BLS series, Size A has no October 2025 value after the lapse in appropriations, and its 2025 annual average uses 11 months. The October 2025 page explains how the calculator handles the gap.