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How Fixed Deposit Interest is Calculated — Compounding, Maturity & Effective Rate

Understand how banks calculate FD interest. Learn about compounding frequency, effective rate vs nominal rate, and how to maximize your fixed deposit returns.

OurDailyCalc Team 5 min read

Fixed Deposits are the backbone of conservative savings in India. You deposit a lump sum, lock it for a tenure, and the bank pays you compound interest. But how exactly is that interest calculated?

The formula

Maturity = P × (1 + r/n)^(n × t)
  • P = Principal (deposit amount)
  • r = Annual interest rate (decimal)
  • n = Compounding frequency (4 for quarterly, 12 for monthly)
  • t = Tenure in years

Nominal rate vs Effective rate

Banks advertise the nominal rate (e.g., 7.0%). But because interest is compounded (usually quarterly), the effective annual rate is slightly higher:

Effective Rate = (1 + nominal/n)^n − 1
7% compounded quarterly: (1 + 0.07/4)^4 − 1 = 7.19%

This means your actual return is 7.19%, not 7.0%.

Worked example

₹5,00,000 at 7% for 3 years (quarterly compounding):

n = 4, r = 0.07, t = 3
Maturity = 5,00,000 × (1 + 0.07/4)^(4×3)
         = 5,00,000 × (1.0175)^12
         = 5,00,000 × 1.2314
         = ₹6,15,700
Interest earned: ₹1,15,700

How compounding frequency affects returns

On ₹5L at 7% for 5 years:

  • Annual compounding: ₹7,01,276
  • Quarterly: ₹7,09,260
  • Monthly: ₹7,10,896

The difference (~₹10K) grows larger with higher principals and longer tenures.

Tax on FD interest

FD interest is fully taxable as “Income from Other Sources.” TDS is deducted at 10% if annual interest exceeds ₹40,000 (₹50,000 for seniors). Submit Form 15G/15H if your total income is below taxable limits.

Tips to maximize FD returns

  1. Compare across banks — Rates vary by 0.5–1% between banks
  2. Senior citizen rates — Usually 0.5% higher
  3. Laddering — Split into multiple FDs with different tenures for liquidity
  4. Tax-saver FDs — 5-year lock-in with 80C deduction (old regime)

Calculate your FD maturity with the OurDailyCalc FD calculator.

TL;DR

  • FD uses compound interest — interest earns interest
  • Quarterly compounding is most common in India
  • Effective rate is slightly higher than the advertised nominal rate
  • FD interest is fully taxable — plan accordingly
#fd #fixed deposit #interest #banking #savings
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OurDailyCalc Team

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