Inflation calculator

What inflation does to a rupee

Inflation is a persistent rise in the general price level. If a household basket costs ₹100 today and the basket's price rises 6 per cent a year, the same basket costs ₹106 next year and ₹112.36 the year after that. The basket is unchanged; the rupee's buying power is lower, by about 5.66 per cent each year on a reverse reading. The two sides of the same equation drive the two modes on this page.

What rate to use matters more than any technique. Headline CPI, core CPI and your own inflation can sit at different levels in the same year. The page takes a single annual rate because a long-horizon plan rarely benefits from a monthly series; the rate is the user's assumption, not a forecast, and the sensitivity of the output to it is on the page below.

The formula this page uses

Both modes rely on the same compound factor. For a cost today C and an annual rate g, the cost in year n is C multiplied by one plus g, raised to the power n. In the future-cost mode, the page returns that figure. In the buying-power mode, the page divides a future amount by the same factor to get its value in today's rupees.

The index chart holds both together. Each series starts at 100 at year 0: the cost series rises above 100 and the buying power series falls below it, so a reader can see the two curves on a single y-axis and read the gap without flipping scales. The year-by-year table under the chart shows the rupee value of your inputs at every year, in both modes, and the two index levels for a second read.

Worked example you can check

Take ₹10,000 today, 6 per cent annual inflation, a 10-year horizon.

Raising the horizon to 20 years at the same rate pushes the compound factor to 3.2071, and ₹10,000 today becomes ₹32,071. A plan written in today's rupees and run for twenty or thirty years without this adjustment can under-size the goal by a large margin.

The two modes side by side

The future-cost mode answers: what will a known expense cost later? It fits goal-setting work such as a child's course fee, an annual medical outlay or a car replacement. The buying-power mode answers: what will a known future amount buy in today's rupees? It fits reading back a maturity value, a corpus or a contracted future payment into today's language.

Both are the same arithmetic. One uses the compound factor on the numerator, the other on the denominator. Switching the tab on the page swaps the input label, the active chart series and the arithmetic in the working line, so the reader can see exactly which direction the number moves.

India's inflation today

MoSPI's latest release puts headline CPI at 5.54 per cent year-on-year for September 2026 (combined, rural plus urban), with a food sub-index that ran higher. The CPI series was rebased in January 2026 to a 2024 = 100 base; the new series index levels are not comparable with the old 2012 = 100 series, so year-on-year change is the right comparison between the two.

The RBI's statutory inflation target is 4 per cent, with a tolerance band of 2 per cent to 6 per cent (that is, 4 plus or minus 2 percentage points). The framework is set under the RBI Act 1934, section 45ZA. The current review period runs 1 April 2026 to 31 March 2031. This page does not state a long-run average of Indian CPI, because the series changed base in 2026 and old and new index levels are not comparable.

Rule of 72 and the exact log doubling

The rule of 72 says that money loses half its buying power in about 72 divided by the inflation rate. At 6 per cent, 72 divided by 6 is 12 years. The exact figure is the natural log of 2 divided by the natural log of one plus the rate, which at 6 per cent is 11.90 years. So the rule reads 0.10 years high at that rate.

The rule drifts a little more at higher rates and a little less at lower rates, because the log function is not linear. At 8 per cent the rule gives 9.00 years and the exact doubling is 9.01 years, almost the same. At 3 per cent the rule gives 24 years and the exact doubling is 23.45 years. The page prints both side by side with the arithmetic error, so the mental rule can be used with its own size known.

Personal inflation is not CPI

Headline CPI is a national basket. Any one household's spending mix is different. A household spending heavily on school and college fees will see education-services inflation, not the same as the general CPI. A household supporting an older member often tracks medical-services inflation, which has run at a different pace from the headline over long windows. Rent, food and fuel each move on their own schedule.

For a personal plan, the right answer is often not the published number. Treat the input on this page as your own blended rate, not the headline, and run the calculator at a one point either side of that rate as a check. The page does not state a specific figure for education or medical inflation, because any such figure would need a dated primary source.

What this calculator leaves out

• Deflation. A negative inflation rate is outside the 0 per cent to 20 per cent input range; the formula still works for a reader who reads the result in reverse.
• A rate that changes over the horizon. The arithmetic uses a single rate from year 0 to year n.
• Taxes. The page is an arithmetic view of price change, before any income tax, capital gains or indirect tax.
• Currency effects. A purchase priced in a foreign currency depends on the exchange rate as well as the local inflation; this page is a single-currency view.
• Shrinkflation and basket change. A basket's contents change over time, which can under-state the real-world rise in cost for the same utility.

Frequently asked questions

Courses that teach the subject behind the inflation calculator