Understanding Loan Amortization: Why You Pay More Interest Early

Open the amortization schedule of any home loan and you’ll see something disturbing: in the first year, almost all of your EMI goes toward interest. The principal portion is tiny. This isn’t a scam — it’s pure mathematics, and once you understand it, your loan strategy will change.

The math of an EMI

Each EMI splits into two parts: interest on the outstanding balance for that month, and principal repayment. Since the outstanding balance is highest at the start, the interest portion is largest at the start. As the balance shrinks, less interest is owed, and more of each EMI goes to principal.

A concrete example

On a ₹50 lakh, 20-year loan at 9%, the EMI is about ₹45,000. In month 1, interest is ₹37,500 (9%/12 of ₹50L) and principal is just ₹7,500. By month 240, the split has reversed: tiny interest, almost all principal.

Why this matters for prepayment

A prepayment in year 1 reduces the principal balance on which all future interest is calculated. So a ₹1 lakh prepayment in month 12 saves vastly more than the same prepayment in month 180. As a rule of thumb: every prepayment in the first 5 years saves roughly 3x its value in future interest.

The optical illusion

After paying EMIs for 5 years on a 20-year loan (25% of the tenure), you might expect to have paid down 25% of the principal. In reality, you’ve paid down only about 11–13%. This is amortization at work — and it’s why front-loaded prepayment is the single highest-return move in personal finance.