Australia: the worst year was not the 1970s
Ask an Australian when inflation was at its worst and you will usually hear the mid-1970s. The series on this page disagrees. Its highest annual average is 1951, at 19.4%, with 1952 close behind at 17.2%. The famous 1975 figure is 15.2%.
The cause was the Korean War wool boom, which briefly made Australian wool extraordinarily valuable and pushed money through a small economy faster than it could absorb. Converting an amount from the late 1940s therefore crosses a spike most people do not know is there, and a sum from 1950 is worth far more in today's money than the following decade would suggest.
A note on which figure you are comparing. This page uses annual averages. Australian inflation is more often quoted as the year-ended change to a particular quarter, which for March 1975 gives 17.5% and for December 1951 gives a still higher number. Both are correct on their own basis, and the annual average is the one this calculator produces.
The GST put three points into the index, then took them out again
On 1 July 2000 the goods and services tax arrived, and it shows up in the data as cleanly as any policy change ever does. The September quarter of 2000 rose 3.7% in a single quarter. Year-ended inflation reached 6.1% by June 2001, against 3.1% on the ABS series that strips the tax change out: a wedge of about three percentage points.
Then it vanished. By the September quarter of 2001, exactly four quarters on, the headline had fallen back to 2.5% and matched the ex-tax series again.
If your conversion spans mid-2000 to mid-2001, roughly three points of what it reports is a one-off change in the tax system rather than a change in the cost of living.
Two practical limits at the ends of the series
The series opens in the June quarter of 1922, so 1922 is a three-quarter year and its annual average rests on less data than every year after it. Treat it as the weakest point in the run.
At the other end, Australia no longer publishes a quarterly CPI at all. The ABS moved to a complete monthly CPI from the October 2025 reference month, using September 2025 as the link period, and rebased the index to September 2025 = 100 from the old 2011-12 base.
One thing that does not interrupt the series: decimal currency on 14 February 1966 set the dollar at ten shillings, so a pound became two dollars at a fixed ratio. The index chains through it, but a price remembered in pounds, shillings and pence must be converted before you enter it.