Inflation, and the two questions people mix up
The difference between what something will cost and what your money will buy, why your personal inflation rate is not the headline figure, and what it means for a retirement number.
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In short
- There are two separate calculations. What will ₹1 lakh of expenses cost in twenty years, and what will ₹1 lakh saved today be worth then. They are not the same number.
- At 6%, ₹1,00,000 of spending becomes ₹3,20,714 in twenty years, while ₹1,00,000 held still falls to ₹31,180 of purchasing power.
- Your personal inflation rate is set by what you actually buy. Education and healthcare have run well above the headline CPI for two decades.
- A nominal return means nothing until inflation is subtracted. A 7% deposit taxed at 30% against 5% inflation is a real loss.
- Retirement figures are the calculation most sensitive to this, because the horizon is longest and the error compounds throughout.
Inflation is the rate at which prices rise, and therefore the rate at which money loses purchasing power. Those are the same phenomenon described from two directions, and confusing the two directions is where most inflation calculations go wrong.
The two questions
Forward: what will this cost? Multiply by (1 + rate)^years.
Backward: what will my money buy? Divide by the same factor.
At 6% over twenty years the factor is 3.207. Something costing ₹1,00,000 today will cost ₹3,20,714. Money worth ₹1,00,000 today will buy what ₹31,180 buys now.
| Years at 6% | ₹1,00,000 of spending will cost | ₹1,00,000 held still will buy |
|---|---|---|
| 5 | ₹1,33,823 | ₹74,726 |
| 10 | ₹1,79,085 | ₹55,839 |
| 20 | ₹3,20,714 | ₹31,180 |
| 30 | ₹5,74,349 | ₹17,411 |
Both columns describe the same 6%. The asymmetry — prices tripling while purchasing power falls to under a third — is simply the difference between multiplying and dividing by the same number, and it is the reason inflation feels worse than the headline rate suggests.
Your rate is not the headline rate
The Consumer Price Index is a weighted basket meant to represent an average household. You are not an average household.
The weights matter enormously. Food is roughly 46% of the Indian CPI basket. If you spend a smaller share on food and a larger share on school fees, rent and medical care, your personal inflation rate is materially higher than the published figure, and it has been for years.
Approximate long-run trends in India:
| Category | Typical annual rise |
|---|---|
| Headline CPI | 5–6% |
| Food and staples | 4–7%, highly variable |
| Rent, urban | 6–8% |
| School and college fees | 8–12% |
| Private healthcare | 10–14% |
Anyone planning for a child's education or for medical costs in retirement should use the category rate, not the headline one. A twenty-year education plan built on 6% when fees rise at 10% will fall short by more than half, and no amount of investment return chosen later will recover a target that was set too low at the start.
Real return: the only number that matters
A nominal return is what the statement says. A real return is what it buys.
real return ≈ nominal return − inflation
The exact form is (1 + nominal) ÷ (1 + inflation) − 1, which matters at high rates and barely at low ones.
| Instrument | Nominal | After 30% tax | Less 5% inflation |
|---|---|---|---|
| Savings account | 3.0% | 2.10% | −2.90% |
| Fixed deposit | 7.0% | 4.90% | −0.10% |
| PPF (tax free) | 7.1% | 7.10% | +2.10% |
| Equity, long run | 12.0% | 10.80% | +5.80% |
The fixed deposit row is the one worth sitting with. It is entirely safe, it is fully guaranteed, and in the top tax bracket it preserves purchasing power and no more. That is not an argument against fixed deposits — for money needed in two years it is exactly right — but it is a complete argument against holding a thirty-year horizon in one.
The PPF row shows what the tax exemption is actually worth: the same rate as the deposit, and a real return that is positive rather than zero.
The retirement number
This is where inflation does the most damage, because the horizon is longest and the error compounds the whole way.
Someone aged 35 spending ₹50,000 a month today will need roughly ₹2,14,594 a month at 60, at 6% inflation. That is the figure the retirement corpus must support — not ₹50,000.
And the corpus must keep growing after retirement, because prices do not stop rising on the day the salary does. A retirement lasting twenty-five years sees the required monthly amount more than quadruple again across it. Planning a fixed monthly income against a rising cost of living is the most common structural error in Indian retirement planning, and annuity products that pay a level amount for life have exactly this shape.
The usual fix is to plan a withdrawal rate that rises with inflation and to keep a meaningful equity allocation into retirement, rather than moving everything into deposits at 60.
Deflation, and why it is worse
Falling prices sound like good news and are not. If prices are expected to fall, spending is deferred, which reduces demand, which reduces prices further. Debt becomes heavier in real terms because the amount owed is fixed while the money to repay it becomes scarcer.
Japan spent most of three decades on this problem. It is the reason central banks target a small positive inflation rate — the RBI's mandate is 4% with a band of 2% to 6% — rather than zero. A little inflation is a buffer against a much worse condition.
Using the calculator honestly
Choose the rate for the thing. Headline CPI for general spending; a higher figure for education, healthcare and urban rent.
Model a range, not a point. Indian inflation has averaged near 6% over two decades but has been above 10% and below 4% within that. Run 5% and 8% and see how much the plan depends on the difference.
Do not mix nominal and real. Either inflate the goal and use a nominal return, or leave the goal in today's prices and use a real return. Doing one of each is how people arrive at a target three times too large or a third of what they need.
Remember that income inflates too. Salaries in India have broadly outpaced CPI, so a fixed savings amount is a shrinking one in real terms. A contribution that rises annually is the natural counterpart to a cost that does.
How the index is actually built
The Consumer Price Index is a weighted average of price changes across a fixed basket of goods and services, collected monthly from a sample of markets across India and published by the National Statistical Office.
Two features of that construction explain most of the gap between the published figure and lived experience.
The basket is fixed between revisions. Weights are updated only when the base year changes, which happens roughly once a decade. Spending patterns move faster than that, so the index lags real consumption — data plans, food delivery and online services entered household budgets long before their weights did.
Substitution is not captured. When the price of one item rises sharply, people buy less of it and more of something else. A fixed basket keeps charging the full weight, which tends to overstate inflation. Working against that, quality improvements are hard to price: a phone costing the same as five years ago is a considerably better phone, and the index struggles to record that as a price fall.
There is also core inflation, which strips out food and fuel because they are volatile and driven by weather and global oil rather than domestic demand. The RBI watches core when setting policy, and households experience headline. Both are correct measures of different things, which is why the rate on the news and the rate at the shop can diverge for months at a time without either being wrong.
For personal planning, none of this argues for a different number so much as for a range. Model 5% and 8% and see which decisions actually change.
What this calculator assumes
- A constant inflation rate across the whole period, which no real economy has ever produced.
- The forward figure is what an amount of spending will cost; the backward figure is what an amount of money will buy. Both use the same rate.
- The rate you enter should reflect the category being modelled, not the headline CPI, unless general spending is what you mean.
- No tax, income growth or return on the money is included — those belong in the savings and investment calculators.
- Historical Indian CPI has averaged roughly 6% over the last two decades, which is a reasonable default and not a forecast.