Glossary
Index ratio
Comparison-month index divided by base-month index. The heart of a CPI adjustment.
The index ratio is index_comparison ÷ index_base. Subtract 1 for the raw percent. Multiply the price by the ratio, or by 1 plus the percent after a floor or cap has replaced the raw percent.
Example, using published levels. CPI-U U.S. city average (CUUR0000SA0) was 324.800 in September 2025 and 336.940 in September 2026. The ratio is 336.940 ÷ 324.800 = 1.037377. On a $3,000 fee with no floor and no cap, the adjusted fee is $3,112.13 after rounding half-up to the cent. The raw change is 3.738%, not whatever rounded headline was in the news that morning.
Apply a cap or a floor to the percent, then recompute the price from the clamped percent. Do not apply the cap to the index level itself.
Round money at the end unless the contract says to round each anniversary to the cent and then compound, which is a different and also legitimate instruction. Say which one you did on the worksheet.
Related terms
See it used in a worked example · CPI calculator · Request an audit
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.