What is a Fixed Deposit?
A fixed deposit (FD) is one of the simplest and safest ways to grow your savings. You deposit a lump sum of money with a bank for a fixed period of time — say 1 year or 5 years — and in return, the bank pays you a guaranteed rate of interest.
Unlike a savings account where you can withdraw money anytime, a fixed deposit locks your money in for the agreed term. Because the bank can rely on having your money for that period, they reward you with a higher interest rate than a regular savings account.
Key Features of a Fixed Deposit
| Feature | Details |
|---|---|
| Deposit period | Typically 7 days to 10 years |
| Interest rate | Fixed for the entire term (usually 4–12% p.a.) |
| Risk level | Very low — guaranteed by the bank |
| Liquidity | Low — early withdrawal usually incurs a penalty |
| Minimum deposit | Varies by bank (often $500–$1,000) |
How is FD Interest Calculated?
Interest on a fixed deposit is calculated based on three things:
- Principal (P) — the amount you deposit
- Interest Rate (r) — the annual percentage the bank offers
- Time (t) — how long you lock in your money, in years
Banks calculate interest using one of two methods: simple interest or compound interest. Understanding the difference can significantly affect how much your money grows.
Simple Interest — The Basics
With simple interest, the bank pays you interest only on your original deposit (the principal). The interest amount is the same every year — it does not grow on itself.
For example: if you deposit $10,000 at 8% for 5 years, your interest each year is $800. After 5 years, you earn $4,000 in total interest — simple and predictable.
What is Compound Interest?
Compound interest is where things get powerful. Instead of earning interest only on your original deposit, you earn interest on your interest too. Your earnings are added back to your balance, and then the next period's interest is calculated on that larger balance.
Albert Einstein reportedly called compound interest "the eighth wonder of the world" — and for good reason. Over long periods, it can turn a modest deposit into a significantly larger sum.
Where n = number of times interest is compounded per year
Compounding Frequency Matters
The more frequently interest is compounded, the more you earn. A 10% rate compounded monthly will earn you slightly more than 10% compounded annually.
| Compounding Frequency | Times per year (n) | Effect on returns |
|---|---|---|
| Annually | 1 | Baseline |
| Quarterly | 4 | Slightly higher |
| Monthly | 12 | Higher still |
| Daily | 365 | Highest (marginally) |
A Real Example with Numbers
Let's say you deposit $10,000 in a fixed deposit at 8% annual interest for 5 years, compounded annually. Here's exactly what happens each year:
Notice that the interest earned each year is slightly more than the last — because you're earning interest on a growing balance, not just your original $10,000.
Compound vs Simple Interest: The Real Difference
Using the same example ($10,000 at 8% for 5 years), here's how the two methods compare:
| Method | Total Interest | Maturity Amount |
|---|---|---|
| Simple Interest | $4,000 | $14,000 |
| Compound Interest | $4,693 | $14,693 |
| Difference | +$693 | +$693 |
$693 extra might not seem huge over 5 years — but extend that to 20 or 30 years and the gap becomes dramatic. Compound interest rewards patience.
Ready to see exactly how much your deposit will grow? Use our FD Calculator to get instant results with your exact numbers.