CPI-U · not seasonally adjusted
Chicago-Naperville-Elgin
CPI-U, All items, Chicago-Naperville-Elgin, IL-IN-WI. Index base 1982-84=100. Published every month.
Latest comparable change: 2.937%, from 304.472 in September 2025 to 313.415 in September 2026. On a fictional $3,000 fee with no floor and no cap, that ratio produces 3088.12. The cap in the contract can reduce it. The floor can raise it. This page does not apply either.
Open these two months in the calculator.
Index levels since 2019
| Month | Index | Change vs. year earlier |
|---|---|---|
| September 2026 | 313.415 | 2.937% |
| August 2026 | 310.890 | 2.389% |
| July 2026 | 309.462 | 2.515% |
| June 2026 | 309.915 | 2.471% |
| May 2026 | 312.867 | 3.719% |
| April 2026 | 309.364 | 3.127% |
| March 2026 | 306.592 | 2.255% |
| February 2026 | 304.489 | 2.021% |
| January 2026 | 302.224 | 1.345% |
| December 2025 | 301.159 | 2.172% |
| November 2025 | 301.839 | 2.477% |
| September 2025 | 304.472 | 2.869% |
| August 2025 | 303.636 | 3.064% |
| July 2025 | 301.871 | 2.697% |
| June 2025 | 302.442 | 3.538% |
| May 2025 | 301.650 | 3.261% |
| April 2025 | 299.983 | 3.116% |
| March 2025 | 299.831 | 3.723% |
| February 2025 | 298.457 | 3.849% |
| January 2025 | 298.213 | 4.262% |
| December 2024 | 294.757 | 3.875% |
| November 2024 | 294.542 | 3.763% |
| October 2024 | 295.239 | 3.516% |
| September 2024 | 295.979 | 4.081% |
| August 2024 | 294.608 | 3.751% |
| July 2024 | 293.943 | 3.673% |
| June 2024 | 292.106 | 2.989% |
| May 2024 | 292.123 | 3.073% |
| April 2024 | 290.918 | 3.008% |
| March 2024 | 289.069 | 3.136% |
| February 2024 | 287.394 | 3.387% |
| January 2024 | 286.022 | 3.264% |
| December 2023 | 283.760 | 3.344% |
| November 2023 | 283.859 | 2.528% |
| October 2023 | 285.211 | 2.441% |
| September 2023 | 284.375 | 2.282% |
| August 2023 | 283.957 | 2.344% |
| July 2023 | 283.528 | 2.242% |
| June 2023 | 283.627 | 2.105% |
| May 2023 | 283.415 | 3.323% |
| April 2023 | 282.423 | 4.768% |
| March 2023 | 280.279 | 4.419% |
| February 2023 | 277.978 | 4.965% |
| January 2023 | 276.982 | 5.425% |
| December 2022 | 274.577 | 5.457% |
| November 2022 | 276.861 | 6.791% |
| October 2022 | 278.415 | 7.654% |
| September 2022 | 278.030 | 8.233% |
| August 2022 | 277.454 | 8.347% |
| July 2022 | 277.311 | 8.355% |
| June 2022 | 277.780 | 8.944% |
| May 2022 | 274.301 | 8.021% |
| April 2022 | 269.569 | 7.188% |
| March 2022 | 268.417 | 7.805% |
| February 2022 | 264.828 | 7.050% |
| January 2022 | 262.730 | 6.797% |
| December 2021 | 260.368 | 6.606% |
| November 2021 | 259.254 | 5.987% |
| October 2021 | 258.621 | 5.309% |
| September 2021 | 256.881 | 4.532% |
| August 2021 | 256.078 | 4.804% |
| July 2021 | 255.929 | 4.869% |
| June 2021 | 254.974 | 4.723% |
| May 2021 | 253.934 | 4.650% |
| April 2021 | 251.491 | 4.629% |
| March 2021 | 248.984 | 2.608% |
| February 2021 | 247.387 | 1.219% |
| January 2021 | 246.008 | 0.674% |
| December 2020 | 244.235 | 0.891% |
| November 2020 | 244.610 | 0.803% |
| October 2020 | 245.584 | 0.965% |
| September 2020 | 245.745 | 1.383% |
| August 2020 | 244.341 | 0.974% |
| July 2020 | 244.046 | 1.017% |
| June 2020 | 243.475 | 1.096% |
| May 2020 | 242.650 | 0.369% |
| April 2020 | 240.364 | 0.266% |
| March 2020 | 242.655 | 1.098% |
| February 2020 | 244.407 | 1.977% |
| January 2020 | 244.361 | 2.579% |
| December 2019 | 242.079 | — |
| November 2019 | 242.661 | — |
| October 2019 | 243.236 | — |
| September 2019 | 242.393 | — |
| August 2019 | 241.985 | — |
| July 2019 | 241.589 | — |
| June 2019 | 240.835 | — |
| May 2019 | 241.758 | — |
| April 2019 | 239.726 | — |
| March 2019 | 240.019 | — |
| February 2019 | 239.669 | — |
| January 2019 | 238.218 | — |
Where this series is relevant
Questions
What is the latest Chicago-Naperville-Elgin CPI-U change?
From September 2025 (304.472) to September 2026 (313.415), the index change is 2.937%. That is the raw change before any contractual floor or cap.
Can this series be used for any contract in Illinois?
Only if the contract names this area, or names this series. A clause that says CPI without a geography is ambiguous. The U.S. city average is a different series.
Sources and limits
Index levels from the U.S. Bureau of Labor Statistics Consumer Price Index, not seasonally adjusted, retrieved through the BLS Public Data API on November 1, 2026. Values are index points, not the headline 12-month percent.
Statewide rates reflect U.S. Department of Labor state minimum-wage postings as updated January 1, 2026, the U.S. Department of State Diplomatic Note on 2026 increases, and, for the prior-year comparison and named local rates, the National Employment Law Project compilation published in November 2025. Confirm the rate that applies to the workplace before using it in a bill.
The contracts in these worksheets are fictional. The prices are chosen so the arithmetic is easy to check. They are not a price survey and they are not client results.
RateClause is not a law firm. Nothing on this page is legal advice. Your clause controls, including whether a past period can be rebilled at all.
Primary postings: BLS Consumer Price Index, U.S. Department of Labor, state minimum wages, U.S. Department of State notice of 2026 minimum-wage increases.