How do I calculate the CPI?
Work out a consumer price index from what a basket of goods costs now and in a base period, or the price change between two CPI values. Type the CPIs yourself, or pick two years and the CPI calculator uses the BLS CPI-U yearly averages from 1913 to 2025.
- Consumer price index (CPI)
- 109.813
The price change between the two periods is 9.81%.
- Inflation (price change)
- 9.81%
Consumer price index (CPI): 109.813. The price change between the two periods is 9.81%.
The results are estimates for information only. They are not financial, tax, or legal advice. Check the numbers with your lender or a qualified professional before you decide. Terms of use
How to calculate
Computes a consumer price index from the cost of a basket of goods, and the inflation between two CPI values, typed or the BLS CPI-U yearly averages since 1913.
Example with the default inputs (I know Basket costs, Cost of the basket in the base period $107.00, Cost of the same basket now $117.50): The price change between the two periods is 9.81%.
Method: CPI = cost of the basket now ÷ cost in the base period × 100. Price change = (later CPI − earlier CPI) ÷ earlier CPI × 100. Amount at later prices = amount × later CPI ÷ earlier CPI. Average yearly rate = (CPI of the later year ÷ CPI of the earlier year)^(1 ÷ years between them) − 1, the same whichever year is typed first.
- The basket holds the same goods and services in the same amounts in both periods; only prices change.
- Both CPI values use the same base, such as the CPI-U with 1982-84 = 100.
- The years are BLS CPI-U yearly averages (all items, US city average, not seasonally adjusted) from 1913 to 2025.
- Arithmetic is exact on the decimals you type; the CPI shows to 3 decimals, percents to 2 and money to the cent, halves up.
Worked examples
Each example is checked against the calculator on every build.
- I know Basket costs, Cost of the basket in the base period $107.00, Cost of the same basket now $117.50 gives Consumer price index (CPI) 109.813, Inflation (price change) 9.81%.Source: OpenStax, Principles of Macroeconomics 3e, 9.1 Tracking Inflation, Tables 9.2 and 9.3 (a basket costs $100, $106.50, $107 and $117.50 in four periods; with period 3 as the base year, index = spending ÷ 107 × 100: 93.4, 99.5, 100, 109.8; inflation from period 1 to 2 is 6.5%). https://openstax.org/books/principles-macroeconomics-3e/pages/9-1-tracking-inflation
- I know Basket costs, Cost of the basket in the base period $100.00, Cost of the same basket now $106.50 gives Consumer price index (CPI) 106.5, Inflation (price change) 6.5%.Source: OpenStax, Principles of Macroeconomics 3e, 9.1 Tracking Inflation, Tables 9.2 and 9.3 (a basket costs $100, $106.50, $107 and $117.50 in four periods; with period 3 as the base year, index = spending ÷ 107 × 100: 93.4, 99.5, 100, 109.8; inflation from period 1 to 2 is 6.5%). https://openstax.org/books/principles-macroeconomics-3e/pages/9-1-tracking-inflation
- I know Two CPIs, Earlier CPI 112.5, Later CPI 121.5 gives Inflation (price change) 8%.Source: U.S. Bureau of Labor Statistics, Consumer Price Index Frequently Asked Questions (percent change = change in index points ÷ starting index × 100: Item A 112.500 to 121.500 is 8.0%, Item C 110.000 to 128.000 is 16.4%). https://www.bls.gov/cpi/questions-and-answers.htm: 9.0 ÷ 112.500 × 100 = 8.0
- I know Two CPIs, Earlier CPI 110, Later CPI 128, Amount in the start period (optional) $100.00 gives Inflation (price change) 16.36%, Amount at the later prices $116.36.Source: U.S. Bureau of Labor Statistics, Consumer Price Index Frequently Asked Questions (percent change = change in index points ÷ starting index × 100: Item A 112.500 to 121.500 is 8.0%, Item C 110.000 to 128.000 is 16.4%). https://www.bls.gov/cpi/questions-and-answers.htm: 18.0 ÷ 110.000 × 100 = 16.4 (exact 16.3636…)
- I know Two years, Start year 2000, End year 2025, Amount in the start period (optional) $100.00 gives CPI-U in the start year 172.2, CPI-U in the end year 321.943, Inflation (price change) 86.96%, Amount at the later prices $186.96, Average inflation a year 2.53%.Source: U.S. Bureau of Labor Statistics, CPI-U, US city average, all items, 1982-84=100, series CUUR0000SA0, yearly averages (2000: 172.2; 2025: 321.943; 1913: 9.9). https://data.bls.gov/timeseries/CUUR0000SA0
- I know Two years, Start year 2025, End year 2000, Amount in the start period (optional) $1,000.00 gives Inflation (price change) −46.51%, Amount at the later prices $534.88, Average inflation a year 2.53%.Source: U.S. Bureau of Labor Statistics, CPI-U, US city average, all items, 1982-84=100, series CUUR0000SA0, yearly averages (2000: 172.2; 2025: 321.943; 1913: 9.9). https://data.bls.gov/timeseries/CUUR0000SA0
- I know Two years, Start year 1913, End year 2025, Amount in the start period (optional) $1.00 gives Amount at the later prices $32.52, Average inflation a year 3.16%.Source: U.S. Bureau of Labor Statistics, CPI-U, US city average, all items, 1982-84=100, series CUUR0000SA0, yearly averages (2000: 172.2; 2025: 321.943; 1913: 9.9). https://data.bls.gov/timeseries/CUUR0000SA0
How it works
From basket costs. Price the same basket of goods and services in two periods:
- CPI = cost of the basket now ÷ cost of the basket in the base period × 100
- Price change = (cost now − base-period cost) ÷ base-period cost × 100, which is the CPI − 100
From two CPI values (typed, or the BLS CPI-U yearly averages of two years):
- Price change (inflation) = (later CPI − earlier CPI) ÷ earlier CPI × 100
- Amount at the later prices = amount × later CPI ÷ earlier CPI, shown when you give an amount
- Average inflation a year (two years only) = ((CPI of the later year ÷ CPI of the earlier year)^(1 ÷ years between them) − 1) × 100: the yearly rate from the earlier year to the later one, which compounds to the price change between them. It is the same whichever year you type first, so it keeps its sign when the end year is before the start year (the price change then shows the other way). It is shown when the years differ.
Rules:
- The base-period cost and both typed CPIs must be more than 0; the cost now and the amount are 0 or more. Each is at most 1 quadrillion.
- The years run from 1913 to 2025. "Earlier" and "later" are labels: a later CPI that is lower gives a negative price change (deflation), and an end year before the start year turns the amount back into the earlier year's prices.
- A result too large to show as a number gives no answer. So does a result that is not 0 but too small to show as a number.
- The arithmetic is exact on the decimals you type, except the average yearly rate, which takes a power. The CPI and the year table values show to 3 decimals (trailing zeros dropped), percents to 2 decimals and money to the cent, with halves rounded up (away from 0).
BLS CPI-U yearly averages, 1982-84 = 100
The CPI-U yearly average for each year from 1913 to 2025, as BLS publishes it (series CUUR0000SA0): one decimal through 2006, three from 2007. Each is the average of the year's monthly indexes. BLS did not collect October 2025 data during the 2025 lapse in appropriations; its 2025 average, 321.943, is the average of the other 11 months.
| Decade | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|---|
| 1910s | 9.9 | 10.0 | 10.1 | 10.9 | 12.8 | 15.1 | 17.3 | |||
| 1920s | 20.0 | 17.9 | 16.8 | 17.1 | 17.1 | 17.5 | 17.7 | 17.4 | 17.1 | 17.1 |
| 1930s | 16.7 | 15.2 | 13.7 | 13.0 | 13.4 | 13.7 | 13.9 | 14.4 | 14.1 | 13.9 |
| 1940s | 14.0 | 14.7 | 16.3 | 17.3 | 17.6 | 18.0 | 19.5 | 22.3 | 24.1 | 23.8 |
| 1950s | 24.1 | 26.0 | 26.5 | 26.7 | 26.9 | 26.8 | 27.2 | 28.1 | 28.9 | 29.1 |
| 1960s | 29.6 | 29.9 | 30.2 | 30.6 | 31.0 | 31.5 | 32.4 | 33.4 | 34.8 | 36.7 |
| 1970s | 38.8 | 40.5 | 41.8 | 44.4 | 49.3 | 53.8 | 56.9 | 60.6 | 65.2 | 72.6 |
| 1980s | 82.4 | 90.9 | 96.5 | 99.6 | 103.9 | 107.6 | 109.6 | 113.6 | 118.3 | 124.0 |
| 1990s | 130.7 | 136.2 | 140.3 | 144.5 | 148.2 | 152.4 | 156.9 | 160.5 | 163.0 | 166.6 |
| 2000s | 172.2 | 177.1 | 179.9 | 184.0 | 188.9 | 195.3 | 201.6 | 207.342 | 215.303 | 214.537 |
| 2010s | 218.056 | 224.939 | 229.594 | 232.957 | 236.736 | 237.017 | 240.007 | 245.120 | 251.107 | 255.657 |
| 2020s | 258.811 | 270.970 | 292.655 | 304.702 | 313.689 | 321.943 |
When the data is out of date
The table ends with 2025. BLS publishes the 2026 yearly average with the December 2026 CPI on January 13, 2027. From that day the page keeps working with the years it has and says "Uses BLS CPI-U yearly averages through 2025" above the result. Years after 2025 are not offered until the table is updated. The basket and typed-CPI modes do not use the table.
Assumptions
- The basket holds the same goods and services, in the same amounts, in both periods; only the prices change. The official CPI weights thousands of prices from a survey of spending, but the idea is the same.
- Two typed CPIs must use the same base. The official CPI-U uses 1982-84 = 100.
Worked examples by hand
A student's basket. The basket costs $107 in the base period and $117.50 now. CPI = 117.50 ÷ 107 × 100 = 109.813…, shown as 109.813. The price change is 9.81%. (OpenStax rounds the index to 109.8.)
One period later. The basket goes from $100 to $106.50: CPI = 106.50 ÷ 100 × 100 = 106.5, a price change of 6.5%.
BLS Item A. The CPI goes from 112.500 to 121.500, up 9.0 points: 9.0 ÷ 112.500 × 100 = 8%.
BLS Item C, with $100. From 110.000 to 128.000 is 18.0 ÷ 110.000 × 100 = 16.3636…, shown as 16.36%. $100 at the earlier prices is 100 × 128 ÷ 110 = $116.36 at the later prices.
$100 in 2000 at 2025 prices. CPI-U 2000 = 172.2 and 2025 = 321.943. Value = 100 × 321.943 ÷ 172.2 = $186.96; the price change is 86.96%. Over 25 years that is (321.943 ÷ 172.2)^(1/25) − 1 = 2.53% a year.
Back in time: $1,000 in 2025 at 2000 prices. Value = 1,000 × 172.2 ÷ 321.943 = $534.88, a price change of −46.51%. The average yearly rate is the same 2.53%.
$1 in 1913. CPI-U 1913 = 9.9: 1 × 321.943 ÷ 9.9 = $32.52 in 2025, or 3.16% a year over 112 years.
Other questions people ask
How do I calculate the CPI?
Price the same basket of goods and services in a base period and in the period you want. Divide the cost now by the cost in the base period and multiply by 100. A basket that cost $107 in the base period and $117.50 now has a CPI of 117.50 ÷ 107 × 100 = 109.81.
How do I calculate inflation from the CPI?
Subtract the earlier CPI from the later one, divide by the earlier CPI and multiply by 100. A CPI that rises from 110.000 to 128.000 has risen 18 points, which is 18 ÷ 110 × 100 = 16.36%.
What does a CPI of 110 mean?
Prices are 10% higher than in the base period, which has an index of 100. The official CPI-U uses 1982-84 = 100, so a CPI-U of 321.943 (the 2025 average) means prices were about 3.2 times their 1982-84 level.
Why use percent changes and not index points?
A rise of 18 points is a bigger change from 110 than from 225. BLS shows both: 225.000 to 243.000 is 8.0% and 110.000 to 128.000 is 16.4%, though both rose 18 points. Percent changes compare across different starting levels.
What is a dollar from one year worth in another?
Multiply the amount by the later year’s CPI and divide by the earlier year’s. With the BLS CPI-U yearly averages, $100 in 2000 (CPI 172.2) equals 100 × 321.943 ÷ 172.2 = $186.96 in 2025.
Which CPI does the year table use?
The CPI for All Urban Consumers (CPI-U), all items, US city average, not seasonally adjusted, 1982-84 = 100: the one BLS reports as the CPI. Each value is the yearly average of the monthly indexes. For a single month, use the inflation calculator, which has every month since 1913.