India: before 2013 this series is wholesale prices, not consumer prices
This is the most important thing to know before converting an old Indian figure. The series is spliced: from January 2013 it follows India's combined consumer price index, but everything before that, back to 1953, is the Wholesale Price Index.
The two measure different things. Wholesale prices track goods at the point of bulk sale, with no services, no house rent and no retail margin. Consumer prices track what a household actually hands over. For most of the twentieth century the wholesale series is the only continuous national price index India had, so it is what any long conversion has to use, but a 1975 or 1990 rupee converted through it answers a question about goods leaving a warehouse rather than about a family's cost of living.
Treat pre-2013 Indian conversions as an approximation of the price level, not a household budget.
There was no single national consumer index until 2011
The reason is not neglect. India measured retail prices carefully, but separately, by occupation: CPI-IW for industrial workers, which still sets dearness allowance and minimum wages; CPI-AL and CPI-RL for agricultural and rural labourers; and CPI-UNME for urban non-manual employees, retired in 2011.
The combined Rural and Urban index that most people now mean by "Indian CPI" was first released in January 2011. It was rebased to 2012=100, and again to 2024=100 in February 2026. So anyone comparing a figure from before 2011 with one from after is crossing not just a rebasing but a change in what was being counted.
For readers over forty there is a further wrinkle: through the 1990s and 2000s the number reported in Indian newspapers as "the inflation rate" was usually the wholesale index, not any consumer one.
Decimalisation changed the subdivision, not the rupee
The paisa arrived on 1 April 1957. Before it, one rupee was 16 annas, so one anna is 6.25 paise. The rupee itself was never redenominated, so the chain runs through cleanly and no conversion factor applies to the amount you enter, only to the units in which you remember it.
For current context: the Reserve Bank targets 4% with a two-point tolerance either side, renewed on 25 March 2026 for a further five years, and Indian inflation touched a record low of 0.25% in October 2025 before rising again.