Investing

Fixed deposit returns explained: the real maturity math

A fixed deposit is the one product where the return really is fixed — and yet the number the bank quotes, the number a calculator shows, and the number that reaches your account are three different figures. Here is exactly where each gap comes from.

What the formula is actually doing

A cumulative fixed deposit takes a lump sum, credits interest at a set frequency, and pays everything back at the end:

The important part is n. A bank quoting an annual rate does not usually credit that interest once a year — most Indian bank FDs compound quarterly by default. Each quarter, interest is calculated on the balance including all the interest credited before it, which is why the maturity value pulls ahead of a simple rate-times-years calculation. Run your own deposit through the FD calculator to see the four common frequencies side by side; this article explains what the output means once you have it.

A worked example, step by step

Take a deposit of ₹5,00,000 booked for 5 years, compounded quarterly, at an illustrative rate of 7% p.a. — used here purely as a round number for the arithmetic, not as a current market rate. Check your bank for the rate actually on offer.

1. Convert the annual rate to a quarterly rate. 7% ÷ 4 = 1.75% per quarter, or 0.0175 as a decimal.
2. Count the compounding periods. 4 quarters × 5 years = 20 periods.
3. Grow the deposit. (1 + 0.0175)²⁰ = 1.414778. That factor is the whole calculation — it says every rupee deposited becomes about ₹1.41 by maturity.
4. Apply it to the principal. ₹5,00,000 × 1.414778 = ₹7,07,389.
5. Separate out the interest. ₹7,07,389 − ₹5,00,000 = ₹2,07,389 of interest earned.

Notice what step 3 tells you. A naive reading of "7% for 5 years" suggests 35% growth, or ₹1,75,000 of interest. The actual figure is ₹2,07,389 — about ₹32,000 more, entirely from interest earning interest across those 20 quarters.

Compounding frequency: real, but smaller than you think

Holding the same ₹5,00,000, 7% and 5 years, only changing how often interest is credited:

Moving from annual to quarterly compounding is worth ₹6,113 here. Moving from quarterly to monthly adds only another ₹1,424. That is the practical lesson: compounding frequency is worth knowing about, but it is a tie-breaker, not a decision driver. A quoted rate even a fraction of a percent higher will out-earn a better compounding frequency almost every time.

The last column is the number worth carrying around. Effective annual yield is what a quarterly-compounded 7% is actually worth over a year: (1.0175)⁴ − 1 = 7.186%. When one bank quotes a rate and another quotes an "annualised yield", they may be describing the same deposit in two different languages — convert both to effective yield before deciding which is higher.

Tax is the largest gap, and no calculator shows it

FD interest is taxable as income at your slab rate. It is not a separate concessional category, and it does not wait until maturity to become taxable — interest accrues as income in each financial year it is earned, even on a cumulative deposit that pays nothing out until the end. Banks also deduct TDS once your interest crosses the prevailing threshold in a financial year, which is a deduction at source, not the final tax; you settle the difference when you file.

Carry the same example forward. If your income puts you in a 30% slab — an assumption for illustration, since your own slab depends on your total income and the regime you are taxed under:

That post-tax outcome works out to a compound annual return of about 5.23% — from a headline rate of 7%. Nearly two full percentage points of the advertised return goes to tax before the money is yours. Any comparison between an FD and a differently-taxed product is meaningless unless both sides are stated post-tax, because the tax treatment can be a bigger difference than the rate.

Cumulative, non-cumulative, and what breaks the assumption

Everything above describes a cumulative FD: interest is reinvested and paid as one amount at maturity. A non-cumulative FD pays interest out to you monthly, quarterly or annually instead. The rate may be identical, but the maturity math is not — money paid out cannot compound, so a non-cumulative deposit returns less in total. It is an income product, not a growth product, and the FD calculator's figure will overstate it.

Three other assumptions in the formula deserve a second look:

• The tenure completes. Breaking an FD early does not simply stop the interest clock. Most banks recalculate the whole deposit at the rate applicable to the tenure you actually completed, then apply a penalty on top — so interest already credited can be reversed at settlement.
• The rate holds only for the booked tenure. It is genuinely fixed until maturity. Renewal is a fresh booking at whatever rate applies that day, and an auto-renewal instruction can move your money to a very different rate without you doing anything.
• The money is locked. Splitting a lump sum into several deposits maturing at staggered dates — laddering — does not change the maturity math on any one deposit, but it means only a slice of your money is exposed to a single rate, and only a slice has to be broken if you need cash.

Common questions

Why is my FD maturity amount higher than rate multiplied by years?

Because a cumulative FD compounds. Simple interest would pay the same amount every period on the original deposit only. Compounding pays interest on the interest already credited, so each quarter starts from a slightly larger base than the last. Over a five-year tenure that gap is thousands of rupees on a lakh-sized deposit, and it widens with both a higher rate and a longer tenure.

Is monthly compounding always better than quarterly?

For the same quoted annual rate, yes — but by less than most people expect. On a five-year deposit the step from quarterly to monthly compounding is worth a fraction of a percent of the maturity value. A quoted rate that is even a little higher will beat a better compounding frequency almost every time, so compare the rate first and the frequency second.

Does the FD calculator show the amount I actually receive?

No. It shows the pre-tax maturity value. FD interest is taxable as income at your slab rate, and banks deduct TDS once your interest crosses the prevailing threshold in a financial year. TDS is a deduction at source, not a final tax — you settle the difference when you file. Your take-home maturity amount is always lower than the calculator figure unless your total income is below the taxable limit.

What actually happens if I break an FD early?

Most banks do not simply stop paying interest from the break date. They recalculate the entire deposit at the rate that applied to the tenure you actually completed, and usually apply a penalty reduction on top of that. So the interest already credited to you can be clawed back in the final settlement. The exact recalculation method and penalty vary by bank — confirm both before booking a long tenure.

Should I book one long FD or several shorter ones?

Splitting a lump sum across several deposits maturing at different times is called laddering. It does not change the maturity math on any single deposit, but it means only part of your money is locked at any one rate, and only part has to be broken if you need cash early. The trade-off is that shorter tenures may carry different rates than longer ones, so laddering can cost you some yield in exchange for flexibility.

Is an FD rate fixed forever, including on renewal?

The rate is fixed for the tenure you book, and that part is genuinely guaranteed. Renewal is a separate booking at whatever rate applies on the renewal date, which may be higher or lower. Auto-renewal instructions can therefore roll your money into a materially different rate without any action from you, so check what your deposit is set to do at maturity.

If you are depositing every month rather than as a lump sum, the compounding works differently — see the RD calculator for the recurring-deposit version. And if you are weighing a guaranteed rate against a market-linked one, how SIP returns are actually calculated shows what an assumed return does to a projection that carries no guarantee at all.

Educational information only, not financial advice. Found an error? Tell us and we will correct it with a dated note.