Suppose you put ₹10,000 somewhere that grows 8% a year. After year one you have ₹10,800. In year two, the 8% is earned on ₹10,800, not just on the original ₹10,000. Each year's gain joins the pile and starts to earn too. That is compounding.
Simple vs compound
With simple interest, you earn 8% of the original ₹10,000 every year: ₹800 a year, so ₹18,000 after 10 years. With compounding, the same 8% gives about ₹21,589 after 10 years, and about ₹46,610 after 20 years. The gap widens as time passes.
The Rule of 72
A quick mental shortcut: divide 72 by the yearly growth rate to estimate how many years it takes for money to double. At 8%, that is about 9 years. At 6%, about 12 years. It is only an estimate.
Why time matters most
Two friends each invest ₹1,000 a month at the same made-up 8% a year. One starts at 20 and stops at 30. The other starts at 30 and continues to 60. The early starter has a good head start, because those first rupees had decades to compound. In real life, rates are not steady, so treat this as an idea, not a promise.
Compounding can work against you
- Debt: unpaid credit card dues grow at a high rate on top of earlier interest.
- Costs: a fee of 1% a year takes a bite from every year's growth, so it adds up over decades.
- Inflation: prices compound too. Growth below inflation means less buying power.
What it does not mean
Compounding does not mean returns are guaranteed or steady. Share and fund values move up and down, and some years are negative. Anyone who promises a fixed "X% every month" is describing something that does not exist in markets. Our guide to stock-tip scams shows why that is a warning sign.