Simple Interest vs Compound Interest โ The Critical Difference
| Feature | Simple Interest | Compound Interest |
|---|---|---|
| Interest earned on | Principal only | Principal + accumulated interest |
| Formula | P ร r ร t | P ร (1+r)แต โ P |
| โน1L at 10% for 10 years | โน1,00,000 interest | โน1,59,374 interest |
| โน1L at 10% for 20 years | โน2,00,000 interest | โน5,72,750 interest |
| Growth curve | Linear (straight line) | Exponential (hockey stick) |
Compound Interest Formula Explained
A = P ร (1 + r/n)โฟแต
Where: A = Final amount, P = Principal, r = Annual interest rate (decimal), n = Compounding frequency per year, t = Time in years.
Compounding Frequency โ Why It Matters
| Compounding | n | โน1L at 10% for 10 years | Difference vs Annual |
|---|---|---|---|
| Annual | 1 | โน2,59,374 | โ |
| Semi-annual | 2 | โน2,65,330 | +โน5,956 |
| Quarterly | 4 | โน2,68,506 | +โน9,132 |
| Monthly | 12 | โน2,70,704 | +โน11,330 |
| Daily | 365 | โน2,71,791 | +โน12,417 |
More frequent compounding = more growth. This is why bank FDs compounded quarterly outperform annual compounding at the same rate โ and why credit card debt compounded daily grows so fast.
The Rule of 72 โ Quick Doubling Calculator
To find how many years to double your money: Years to double = 72 รท Interest Rate
| Rate | Years to Double | Common Example |
|---|---|---|
| 6% | 12 years | PPF, some FDs |
| 8% | 9 years | RBI bonds, senior citizen FD |
| 12% | 6 years | Large-cap equity mutual funds |
| 15% | 4.8 years | Good mid-cap funds historically |
| 18% | 4 years | Credit card debt rate โ works against you! |
Real Wealth Building Examples
| Scenario | Amount Invested | Rate | Years | Final Value |
|---|---|---|---|---|
| โน10,000 lump sum | โน10,000 | 12% | 30 | โน2,99,599 |
| โน1L per year (recurring) | โน30L | 12% | 30 | โน2.41 crore |
| โน5,000/month SIP | โน18L | 12% | 30 | โน1.76 crore |
| โน10,000/month SIP | โน36L | 12% | 30 | โน3.53 crore |
๐ Calculate Your Compound Interest
See exactly how your money grows with our free compound interest calculator!
Calculate Compound Interest โFrequently Asked Questions
Q: How is compound interest different from SIP returns?
SIP returns also use compounding โ but instead of a lump sum, you invest regularly. SIP calculator accounts for each instalment compounding from the date of investment. Both use the same compounding math, but SIP spreads the investment over time (rupee cost averaging), making the formula more complex.
Q: What is the CAGR and how is it related to compound interest?
CAGR (Compound Annual Growth Rate) is the same as compound interest rate โ expressed as the consistent annual rate that would turn an initial investment into the final value over a given period. If โน1 lakh became โน3 lakh in 10 years, CAGR = (3/1)^(1/10) โ 1 = 11.6%.
โ ๏ธ Disclaimer
This article is for educational purposes only and does not constitute financial advice. Consult a qualified financial advisor before making investment decisions.