Short answer: The consumer price index (CPI) is a single number that shows how much the prices of a typical household’s goods and services have changed since a reference year. A rising CPI signals rising inflation, which means your money buys less than it did before. The index affects your money through the cost of living, the purchasing power of the rupee, and the interest rates set by the Reserve Bank of India (RBI).
Last reviewed: 9 November 2026
At a glance
| Term | What it means |
|---|---|
| CPI | Tracks how much the typical household basket has changed in price |
| Fixed basket | The set of goods and services whose cost is measured each period |
| Base-year cost | The cost of the same basket in the reference year |
| Weight | A category’s share of household budgets, which sets how much it counts |
| Purchasing power | How much a unit of currency can buy |
| Repo rate | The RBI’s benchmark rate, which it typically raises when inflation rises above target |
How is CPI calculated?
CPI works by comparing the cost of a fixed basket in two years. The current-year cost of the basket is divided by its base-year cost, and the result is multiplied by 100. The base year is the reference point, so its index value is 100.
Here is a hypothetical example with invented figures. Suppose a basket cost ₹10,000 in the base year and ₹10,800 in the current year. Dividing 10,800 by 10,000 gives 1.08, and multiplying by 100 gives a CPI of 108. The basket now costs 8% more than it did in the base year.
The basket is kept fixed so that the index measures price changes rather than changes in what people buy. The same items are priced each time, so the comparison stays like-for-like.
What goes into the basket?
The CPI basket covers many spending categories, including food, clothing, housing, transport, healthcare and education. Each category gets a weight, which reflects its share of household budgets. A category with a larger weight moves the index more when its prices change.
This means that a sharp rise in the price of a category with a large weight pushes the CPI up more than the same rise in a small category. A household that spends a larger share of its budget on one category will feel changes in that category more strongly than the index suggests.
How does CPI affect the cost of living?
Because CPI tracks the typical household’s spending, a rising CPI means the cost of living is rising. The same set of goods and services costs more than it did in the base year. Your monthly bills, groceries and fees may all go up, even if your income stays the same.
Consider a hypothetical household that spends ₹20,000 a month on the basket. If the CPI rises from 100 to 108, the same spending pattern would cost about ₹21,600 a month, an extra ₹1,600. Figures like these are invented for illustration and will differ for every household.
How does CPI affect the value of your money?
Rising CPI means lower purchasing power for the currency. Each rupee buys a smaller quantity of goods and services than before. A sum of money that stays the same in rupee terms therefore covers less spending each year.
This is the main catch for anyone holding cash or money in fixed-rupee accounts. The number of rupees does not change, but what they can buy does. The CPI tells you how much that erosion has been, on average, for a typical household.
Why does the RBI watch CPI?
When inflation rises above target, the RBI typically raises its benchmark repo rate. A higher repo rate makes borrowing from the central bank costlier, which reduces liquidity in the economy. Banks then tend to pass some of this cost on to borrowers, and loans can become more expensive.
The RBI therefore reads CPI as a signal. A rising index can lead to higher loan rates, which affects anyone with a home loan, car loan or other borrowing. The effect is indirect, but it links the price index to the interest you pay.
What are the limits of CPI?
CPI describes a typical household, not yours. The weights are based on typical budget shares, so if you spend more on one category than the typical household does, your personal inflation rate may differ from the published CPI. A household that spends most of its income on food, for example, will feel food price changes more strongly.
CPI also measures prices, not your income. A rising CPI can be offset by rising wages, but the index itself does not show whether your pay is keeping up. To judge your own position, you need to compare your income and spending with the index.
Frequently asked questions
Does a rising CPI always mean my money is worth less?
A rising CPI means the price of the typical basket has gone up, so each rupee buys less of that basket. Your own situation depends on how your spending and income change over the same period.
Why does the CPI use a fixed basket?
A fixed basket means the same goods and services are priced each time, so the index measures price changes rather than changes in buying habits. This keeps the comparison between years consistent.
How does CPI affect interest rates?
When inflation rises above target, the RBI typically raises its benchmark repo rate. This makes borrowing from the central bank costlier and reduces liquidity, which can push up the cost of loans in the economy.
Sources and last check
Facts in this article were checked against the sources below on 9 November 2026. Rules and figures can change; check the primary source before acting.
- dhan.co (broker education)
- upstox.com (broker education)
- groww.in (broker education)
This article is general information, not investment advice. MyFinanceBandhu is not a SEBI-registered investment adviser.