How FD Interest Is Calculated (Quarterly Compounding)
Most Indian bank fixed deposits compound interest quarterly, using A = P x (1 + r/4)^(4t), where P is your deposit, r is the annual interest rate and t is the tenure in years. Quarterly compounding means your actual, effective annual return is slightly higher than the FD's stated annual rate, since interest earned each quarter starts earning its own interest.
Most Indian bank fixed deposits compound interest quarterly, not once a year. The formula is A = P x (1 + r/4)^(4t), where P is your deposit amount, r is the annual interest rate as a decimal, and t is the tenure in years. Because interest gets added back to the principal every quarter, your actual annual return ends up a little higher than the stated rate.
The formula, explained term by term
P is the principal, the amount you deposit at the start. r is the bank's quoted annual interest rate, written as a decimal (7% becomes 0.07). The 4 represents four compounding periods a year (quarterly), and t is how many years the deposit runs for. A is the maturity amount at the end.
Run this calculation for your own deposit amount, rate and tenure with the FD calculator, or use the compound interest calculator for a more general compounding setup.
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A worked example: Rs 1,00,000 at an assumed 7% for 5 years
Using the formula with P = Rs 1,00,000, r = 0.07 and t = 5: A = 1,00,000 x (1 + 0.07/4)^(4x5) = 1,00,000 x (1.0175)^20, which works out to approximately Rs 1,41,478. That means the interest earned over 5 years is about Rs 41,478, on top of the original Rs 1,00,000 deposit.
| Compounding basis | Amount after 5 years (assumed 7% p.a. on Rs 1,00,000) | Total interest |
|---|---|---|
| Quarterly (typical for FDs) | Rs 1,41,478 | Rs 41,478 |
| Annually | Rs 1,40,255 | Rs 40,255 |
These figures use an assumed 7% annual rate purely to illustrate the formula. They are not a quote from any specific bank, and actual FD rates change frequently and vary by bank, tenure and deposit amount.
Why the "effective" rate is higher than the card rate
The rate a bank advertises, sometimes called the card rate, is the nominal annual rate before compounding is applied. Because quarterly compounding adds interest back to the principal four times a year, the actual annual growth you experience, called the effective annual rate, works out slightly higher. In the example above, a 7% nominal rate compounds to an effective annual rate of about 7.19%.
This gap widens slightly for higher interest rates and for more frequent compounding (monthly compounds to a higher effective rate than quarterly, for the same nominal rate), which is why comparing two FDs by their nominal rate alone can be misleading if they compound on different schedules.
What changes the final maturity amount
- Tenure: a longer tenure means more compounding periods, so the gap between simple and compound growth widens the longer the money stays deposited.
- Compounding frequency: monthly compounding grows an FD slightly faster than quarterly, which itself grows faster than annual compounding, for the same nominal rate.
- Premature withdrawal: withdrawing before maturity usually resets the calculation to a lower rate or applies a penalty, so the numbers above only apply if the deposit runs its full term.
Confirm the numbers before you invest
This explainer uses an assumed 7% rate purely to show how the compounding formula works. Actual FD interest rates vary by bank, tenure, deposit amount and whether you qualify for a senior citizen rate, and they change over time. Confirm the current rate and compounding frequency directly with your bank before making any deposit decision, and consult a financial adviser for guidance specific to your situation.
Checklist for comparing FDs
- Confirm the compounding frequency (quarterly is common, but check, since some schemes compound monthly or pay out interest instead of compounding it).
- Compare effective annual rates, not just the advertised nominal rate, if two options compound differently.
- Factor in the premature withdrawal penalty if there is any chance you might need the money early.
- Check whether interest is paid out periodically (which you could reinvest yourself) or automatically reinvested by the bank, since this changes your own compounding math.
Cumulative versus non-cumulative FDs
A cumulative FD reinvests every quarter's interest back into the deposit, which is the version the formula above describes, and you receive one lump sum at maturity. A non-cumulative FD instead pays out interest to you at regular intervals, monthly, quarterly or annually, rather than compounding it, which means the deposit itself does not grow the way a cumulative FD's principal does.
If your goal is maximum growth and you do not need regular income from the deposit, a cumulative FD generally ends up with a higher total value at maturity for the same rate and tenure, purely because of the compounding effect shown above. If you are weighing an FD against a market-linked option instead, the SIP calculator formula covers the equivalent compounding math for a monthly investment rather than a lump sum.
Why this differs from a savings account
A savings account typically compounds interest, if at all, at a much lower rate and often quarterly as well, but the rate itself is usually far below what a fixed deposit offers for locking money away for a set period. The FD formula above only applies once you commit funds for the FD's specific tenure; a savings account balance you keep withdrawing from does not compound the same way, since compounding assumes the principal stays untouched for each full period.
A note on tax
FD interest is generally taxable as income in India, and banks may deduct TDS above a certain threshold. The calculations in this explainer are before tax, so the amount you actually keep will be lower once tax is accounted for. Check current tax rules on the Income Tax Department's website or with a tax professional, since thresholds and rates can change.
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Frequently asked questions
What is the FD interest formula?
For quarterly compounding, A = P x (1 + r/4)^(4t), where P is the deposit, r is the annual rate as a decimal, and t is the tenure in years.
Do all Indian bank FDs compound quarterly?
Quarterly compounding is common, but not universal. Some schemes compound monthly, some pay out interest periodically instead of compounding it. Always check the specific scheme's terms.
Why is the effective rate higher than the rate the bank advertises?
Because interest earned each quarter is added back to the principal and starts earning its own interest, the actual annual growth (the effective rate) ends up slightly higher than the nominal advertised rate.
Does a longer FD tenure always mean proportionally more interest?
No, it grows a bit faster than proportional, because compounding accelerates over time. A 10-year FD earns more than double what a 5-year FD earns at the same rate, all else equal.
What happens if I withdraw my FD early?
Most banks apply a penalty or a lower effective rate for premature withdrawal, so the maturity figures calculated for the full tenure will not apply if you withdraw early. Check your specific FD's terms.
Sources
- State Bank of India, Retail domestic term deposit rates (checked 2026-09)
- Income Tax Department, Government of India (checked 2026-09)
Rules and limits change. Always check the latest official notification or portal before you submit a form.