How FD Compounding Works — Quarterly vs Monthly vs Annual
What Is Compounding in a Fixed Deposit?
When you open an FD, the bank pays interest on your principal. But with compound interest, the bank also pays interest on interest earned in previous periods. This is what separates a compound FD from a simple interest deposit.
The more frequently interest is compounded, the more you earn.
Compounding Frequencies in Indian FDs
Indian banks offer four standard compounding options:
| Frequency | Interest Calculated | Compoundings/Year |
|---|---|---|
| Monthly | Every month | 12 |
| Quarterly | Every 3 months | 4 |
| Half-Yearly | Every 6 months | 2 |
| Annually | Once a year | 1 |
Most Indian banks default to quarterly compounding. Monthly is offered by some NBFCs and small finance banks.
The Compound Interest Formula
$$A = P \times \left(1 + \frac{r}{n}\right)^{n \times t}$$
Where:
- A = Maturity amount
- P = Principal
- r = Annual interest rate (decimal)
- n = Number of compoundings per year
- t = Tenure in years
Worked Example: ₹1 Lakh FD at 7% for 1 Year
| Compounding | Formula | Maturity Amount | Interest Earned |
|---|---|---|---|
| Annual | 1,00,000 × (1 + 0.07)¹ | ₹1,07,000 | ₹7,000 |
| Half-Yearly | 1,00,000 × (1 + 0.035)² | ₹1,07,122 | ₹7,122 |
| Quarterly | 1,00,000 × (1 + 0.0175)⁴ | ₹1,07,186 | ₹7,186 |
| Monthly | 1,00,000 × (1 + 0.00583)¹² | ₹1,07,229 | ₹7,229 |
Quarterly vs Annual difference: ₹186 on ₹1L. Doesn’t seem like much for 1 year — but over 5 years on ₹10L, the difference grows to over ₹12,000.
Effective Annual Rate (EAR)
The Effective Annual Rate accounts for compounding and lets you compare FDs with different compounding frequencies on an equal basis.
$$\text{EAR} = \left(1 + \frac{r}{n}\right)^n - 1$$
For a 7% FD:
- Annual: EAR = 7.00%
- Half-Yearly: EAR = 7.12%
- Quarterly: EAR = 7.19%
- Monthly: EAR = 7.23%
When comparing FDs from different banks, always compare the EAR (also called XIRR in some contexts), not just the stated annual rate.
Cumulative vs Non-Cumulative FDs
| Type | How Interest Works | Best For |
|---|---|---|
| Cumulative | Interest reinvested; full payout at maturity | Long-term wealth creation |
| Non-Cumulative | Interest paid monthly/quarterly | Regular income (retirees) |
For wealth creation, cumulative FDs always win because reinvested interest compounds.
Tax on FD Interest
FD interest is taxable at your income tax slab rate:
- TDS deducted at 10% if annual interest > ₹40,000
- TDS deducted at 20% if PAN is not provided
- Senior citizens exempt up to ₹50,000 under Section 80TTB
To avoid TDS, submit Form 15G (below 60 years, income below taxable limit) or Form 15H (senior citizens).
Key Takeaways
- Quarterly compounding is the Indian banking standard
- More frequent compounding = higher effective return
- Always compare EAR, not just stated rates
- Cumulative FDs beat non-cumulative for wealth creation
- Use our FD Calculator to compare compounding options instantly