How CPI adjustment works
A consumer price index tracks the cost of a fixed basket of goods and services over time. Divide the index in the later year by the index in the earlier year and you get the factor by which prices rose. Multiply your amount by it:
The index level itself doesn't matter — only the ratio does — which is why indices with different base years (1982–84 = 100 in the US, 2015 = 100 in the UK, 2002 = 100 in Canada) all work the same way.
The data we use
| Country | Index | Years | Publisher |
|---|---|---|---|
| United States | CPI-U, U.S. city average, all items (annual average, 1982–84=100) | 1913–2025 | U.S. Bureau of Labor Statistics, series CUUR0000SA0 |
| United Kingdom | CPI index 00: all items (annual, 2015=100) | 1988–2025 | Office for National Statistics, series D7BT (MM23) |
| Canada | Consumer Price Index, all-items, Canada (annual average, 2002=100) | 1914–2025 | Statistics Canada, Table 18-10-0005-01 (vector v41693271) |
| Australia | CPI All groups, weighted average of eight capital cities (calendar-year mean of quarterly index) | 1949–2025 | Australian Bureau of Statistics, Consumer Price Index (CPI 1.10001.10.50.Q) |
We use annual averages, so “2015” means average prices across 2015 — the right comparison for a salary or a year's spending, but not for a price paid in a particular month. The current year is excluded until a full year of data is published. Australia's figure is the average of the four quarterly index values published by the ABS for each calendar year (our calculation). The UK's official CPI series starts in 1988; for earlier UK comparisons, the ONS publishes the longer-running RPI and modelled historical estimates.
Data was retrieved directly from each statistics office's published series. Each country's figures only make sense in its own currency — to compare across countries, convert first and then apply that country's inflation.
Projecting forward
Switch to “Future — my own inflation rate” to see what today's spending might cost in the future. The calculator compounds your rate yearly: at 3% a year, $100 of spending today needs about $134 in ten years, and $100 kept as cash would buy only about $74 of today's goods. This is a what-if, not a forecast — we deliberately don't pre-fill a rate.
Why your own inflation may differ
- The CPI basket reflects average household spending. If you spend more on rent, energy or food than average, your personal inflation rate can be higher or lower.
- Housing costs are treated differently across countries — for example, owner-occupiers' costs are excluded from the UK CPI headline but included in the CPIH measure.
- Quality changes (a phone that does more for the same price) are adjusted for statistically, which may not match how you feel about prices.
Sources
- United States: U.S. Bureau of Labor Statistics, series CUUR0000SA0 — CPI-U, U.S. city average, all items (annual average, 1982–84=100)
- United Kingdom: Office for National Statistics, series D7BT (MM23) — CPI index 00: all items (annual, 2015=100)
- Canada: Statistics Canada, Table 18-10-0005-01 (vector v41693271) — Consumer Price Index, all-items, Canada (annual average, 2002=100)
- Australia: Australian Bureau of Statistics, Consumer Price Index (CPI 1.10001.10.50.Q) — CPI All groups, weighted average of eight capital cities (calendar-year mean of quarterly index)
Results are estimates based on the figures you enter and the stated assumptions. They are not financial, tax, legal or engineering advice. Spotted a problem? Tell us.