Understanding Loan EMI and Amortization

One payment, two moving parts

An EMI (Equated Monthly Installment) is fixed, but what's inside it is not. Every payment is split between interest — charged on whatever principal is still outstanding — and principal repayment, which is whatever remains of the payment after interest is covered. Early in the loan the outstanding balance is large, so interest eats most of the payment; late in the loan the balance is small, so most of the payment retires principal.

On a $300,000 mortgage over 30 years at 6%, the payment is about $1,799. Of the very first payment, $1,500 is interest and only $299 reduces the loan. It takes until roughly year 19 before the split reaches 50/50. This front-loading is not a lender trick — it is the arithmetic consequence of charging interest on the outstanding balance — but it surprises almost everyone the first time they see an amortization schedule.

What prepayment actually does

Because interest is charged on the outstanding balance, any extra principal payment saves you the interest that balance would have generated for the entire remaining term. Early prepayments therefore punch far above their weight: an extra payment in year 2 of a 30-year loan avoids up to 28 years of interest on that amount; the same payment in year 28 avoids only 2.

Two caveats. Some loans charge prepayment penalties — check before paying extra. And prepaying a cheap loan while carrying expensive debt is backwards: money sent early to a 6% mortgage while a 22% credit card balance sits unpaid costs you the 16-point difference.

The flat-rate trap

When comparing loans, make sure both rates are quoted on the same basis. A "flat rate" charges interest on the original principal for the whole term, ignoring the fact that you are paying the balance down. A 10% flat rate on a 5-year loan works out to roughly an 18% reducing-balance rate — nearly double what it appears to be. Reputable lenders quote the reducing-balance (or APR) figure; if a quoted rate looks surprisingly cheap, this is the first thing to check.

The EMI calculator uses the reducing-balance method throughout, so its output is comparable with any properly quoted loan offer.

Try it yourself

Sources

Figures can change after publication — check the source for current numbers. This guide is general information, not financial or medical advice.