Real Return: What Inflation Quietly Does to Your FD
- The formula
- Tax first, then inflation
- The break-even rate
- Where this leaves a fixed deposit
- The same maths over twenty years
- Three things to do with this
- Where this fits
Subtracting inflation from your return is close enough for a conversation and wrong for a calculation. The error is small at low numbers and grows with both, and it always points the same way: subtraction makes your real return look better than it is.
The bigger problem is the order of operations. Most people take the return, subtract inflation, and then wonder about tax. Tax comes first, and it changes the answer far more than the formula does.
The formula
Subtraction says: real return = nominal − inflation.
The correct relation is:
Real return = ((1 + nominal) ÷ (1 + inflation)) − 1
At 7% nominal and 6% inflation, subtraction gives 1.00%. The formula gives (1.07 ÷ 1.06) − 1 = 0.94%. Six basis points, which nobody will lose sleep over.
At 14% nominal and 9% inflation, subtraction gives 5.00% and the formula gives 4.59%. The gap widens. At 30% and 20%, subtraction says 10% and the truth is 8.33%.
The reason is that inflation applies to the grown amount, not the original one. You are not losing purchasing power on what you started with; you are losing it on what you ended with.
Tax first, then inflation
This is where fixed deposits stop working, and the arithmetic is not close.
₹10,00,000 in a fixed deposit at 7.0%, held by someone on a 30% marginal rate, with inflation at 6%.
| Step | ₹ |
|---|---|
| Interest for the year | 70,000 |
| Tax at 30% | (21,000) |
| After-tax interest | 49,000 |
| After-tax return | 4.90% |
Assumes interest is taxable at the slab rate, a 30% marginal rate before surcharge and cess, and 6% inflation. Interest on a fixed deposit is taxable as it accrues, not only when the deposit matures.
Real return = (1.049 ÷ 1.06) − 1 = −1.04%.
Negative. The deposit grew by ₹49,000 after tax and the purchasing power of the ₹10,00,000 fell by more than that. In rupees of constant purchasing power, the saver is about ₹10,400 poorer after a year in which the bank paid them ₹70,000.
Nothing went wrong. The deposit did exactly what it promised. The loss is structural, and it is invisible because the bank statement only ever shows the ₹70,000.
The break-even rate
What does a deposit have to pay just to stand still?
Required nominal rate = inflation ÷ (1 − tax rate), approximately, which is close enough at these levels.
| Your marginal rate | Rate needed to break even at 6% inflation |
|---|---|
| 0% | 6.00% |
| 5% | 6.32% |
| 20% | 7.50% |
| 30% | 8.57% |
A saver in the highest bracket needs 8.57% from a fully taxable instrument simply to preserve what they had. Deposits at that rate are not generally available in a 6% inflation environment, and that is not an accident: nominal deposit rates tend to sit a little above inflation, not two and a half points above it.
The person in the highest bracket therefore loses purchasing power on deposits almost structurally, while the person paying no tax roughly holds even. The same product, opposite outcomes, and the difference is entirely the tax rate.
Where this leaves a fixed deposit
It does not make deposits useless. It makes them the wrong tool for growth and the right tool for two other jobs.
Certainty over a known short horizon. Money needed in fourteen months for a specific purpose should not be exposed to markets. A small real loss is the price of knowing the amount will be there, and it is a price worth paying.
An emergency fund. The job is instant availability, not return. Judging an emergency fund on real return is judging it on the wrong criterion.
What deposits cannot do is build a corpus over fifteen years for someone on a high marginal rate. Run that at a negative real return and the money shrinks in purchasing power every year, quietly, while the balance rises.
The same maths over twenty years
₹10,00,000, 6% inflation throughout.
| Instrument | After-tax nominal | Nominal value in 20 years | Value in today’s rupees |
|---|---|---|---|
| FD at 7%, 30% bracket | 4.90% | ₹26,03,000 | ₹8,12,000 |
| Instrument returning 10% after tax | 10.00% | ₹67,27,000 | ₹20,98,000 |
Assumes constant rates, constant 6% inflation, annual compounding and no withdrawals. Purchasing power computed by discounting the nominal value at 6% for 20 years.
The deposit more than doubles in rupees and loses nearly a fifth of its purchasing power. That is the whole argument in one row, and it is why the nominal number on a statement is not information until you have adjusted it.
Three things to do with this
Quote returns to yourself after tax. Two instruments with the same headline rate are not equivalent if one is taxed at slab and the other is not.
Use a realistic inflation figure for your own spending. Headline inflation is an average across a basket. If your outgoings are dominated by school fees, healthcare and domestic help, your personal inflation is probably higher, and your real return correspondingly worse.
Set goals in today’s rupees, then inflate them. A ₹50,00,000 target twenty years out is roughly ₹15,60,000 in today’s purchasing power at 6%. Plan against the real number or the plan is describing a different, smaller goal than you think.
Run your own figures through the real return calculator and the inflation future value converter.
Where this fits
- Your own figures: real return calculator · inflation future value converter
- The deposit side: FD calculator
- The equity side: SIP calculator
- A worked long-horizon case: what ₹1 crore will be worth in 20 years
- Measuring what you actually earned: XIRR or CAGR