Simple vs Compound Interest — Why the Difference Matters
Compound interest is the most powerful force in personal finance. Here’s how it differs from simple interest.
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Interest is the cost (or reward) of money over time — but how it’s calculated makes an enormous difference. Understanding compounding is the single most useful idea in personal finance.
Simple interest
Simple interest is calculated only on the original principal. Lend ₹1 lakh at 10% simple interest and you earn ₹10,000 every year — flat, forever. Try it with the simple interest calculator.
Compound interest
Compound interest is calculated on the principal plus all the interest earned so far. So your interest earns interest. That same ₹1 lakh at 10% compounded grows faster each year, because the base keeps getting bigger. See the compound interest calculator.
Why it matters so much
Over short periods the gap is small, but over decades it’s dramatic — this is why starting early is so powerful. A small amount compounding for 30 years can beat a much larger amount compounding for 10. It’s the engine behind SIPs and long-term wealth.
The flip side
Compounding works against you on debt too — unpaid credit-card balances compound against you at high rates. The lesson cuts both ways: let compounding work for you (invest early) and avoid letting it work against you (clear high-interest debt). See what is compounding.
