How to Calculate Loan Amortization (Step by Step) – India

When you take a home loan, car loan, or personal loan in India, you repay it through equal monthly instalments (EMIs). But each EMI is not a simple slice of the loan — it is split between interest and principal, and that split changes every month. Understanding this split, called amortization, helps you see how much of your money is actually reducing your debt and when prepayment will help most. This guide shows you exactly how to calculate a loan amortization schedule step by step.

You can build the full schedule by hand for learning, or generate it instantly with our free loan amortization calculator. Either way, the logic below is the same one every Indian bank and NBFC uses.

Key takeaway: An EMI stays fixed, but the interest portion shrinks and the principal portion grows every month — that is the whole idea behind amortization.

What Is a Loan Amortization Schedule?

An amortization schedule is a month-by-month table showing, for each EMI, how much goes to interest, how much reduces the principal, and what balance remains. At the start of a loan the outstanding balance is large, so the interest portion is high and little principal is repaid. As the balance falls, interest reduces and more of each EMI chips away at the principal. By the final EMI, almost the entire payment is principal.

Step 1: Calculate the EMI

Before building the schedule, you need the EMI. The standard formula is EMI = P × r × (1+r)^n / ((1+r)^n − 1), where P is the principal (loan amount), r is the monthly interest rate as a decimal (annual rate ÷ 12 ÷ 100), and n is the number of monthly instalments. For example, a home loan rate of 8.5% per year gives a monthly rate of about 0.007083.

Step 2: Work Out the First Month’s Interest

For the first month, the interest is the full outstanding balance multiplied by the monthly rate. On a ₹30,00,000 loan at 8.5% per year, the first month’s interest is 30,00,000 × 0.007083, which is about ₹21,250. Whatever remains of the EMI after this interest is the principal repaid that month.

Step 3: Find the Principal Repaid and New Balance

Subtract the month’s interest from the EMI to get the principal repaid, then subtract that principal from the outstanding balance to get the new balance. If the EMI is about ₹26,035, then in month one roughly ₹4,785 goes to principal and the balance falls to about ₹29,95,215. Notice how small the principal portion is at first — this is why the early years of an Indian home loan feel like you are “only paying interest.”

Step 4: Repeat for Every Month

Repeat the same three steps for each subsequent month, always using the reduced balance to compute that month’s interest. Because the balance keeps falling, the interest portion shrinks and the principal portion grows, month after month, until the balance reaches zero at the end of the tenure. This repeating calculation is exactly what the calculator automates.

A Simplified Amortization Table

The pattern is clear: interest dominates early and principal dominates late.

The India Angle: Repo Rate and Floating EMIs

Most Indian home loans are floating rate, linked to an external benchmark — usually the RBI repo rate — plus a bank spread. Your rate is roughly Repo Rate + Spread; with the repo rate around 5.25% in 2026 and a typical spread, home loan rates hover near 8.5%. Banks must reset external-benchmark rates at least every three months, so a repo change flows into your loan quickly. Often the bank keeps your EMI the same and changes the tenure instead, which reshapes your amortization schedule.

Benefits of Understanding Amortization

Knowing your amortization schedule helps you make smarter money decisions. You can see exactly how much interest you will pay over the life of the loan, decide when to prepay for maximum savings, and understand why a longer tenure lowers the EMI but raises total interest. For tax planning, it also shows the interest paid each year, which matters for the Section 24(b) deduction on home loan interest of up to ₹2 lakh a year.

Common Mistakes to Avoid

1. Using the annual rate directly instead of converting it to a monthly rate.
2. Forgetting that early EMIs are mostly interest, so late prepayment saves little.
3. Assuming a fixed EMI means fixed interest — floating rates change the split.
4. Ignoring processing fees and insurance that raise the effective cost.
5. Overlooking that extending tenure after a rate hike increases total interest.
6. Not checking whether prepayment charges apply, especially on non-floating loans.

Best Practices and Expert Recommendations

1. Prepay in the early years, when the interest portion is highest.
2. Compare total interest, not just the EMI, when choosing a tenure.
3. Track repo-rate changes, since floating EMIs or tenures will adjust.
4. Use the yearly interest figure for your Section 24(b) tax claim.
5. Keep an emergency buffer before making large prepayments.
6. Verify your bank’s schedule against a reliable EMI calculation.

Worked Example

Suppose Anita takes a ₹30,00,000 home loan at 8.5% for 20 years (240 months). Her EMI works out to about ₹26,035. In the first month, about ₹21,250 is interest and only ₹4,785 reduces the principal. Over 20 years she pays roughly ₹32.5 lakh in interest — more than the loan itself. If she prepays ₹2 lakh in year two, she cuts several years and lakhs of rupees off her interest, precisely because early prepayment attacks the interest-heavy part of the schedule.

How a Repo-Rate Change Reshapes Your Schedule

Because most Indian home loans are on a floating rate, a change in the Reserve Bank of India policy rate flows through to your loan within a few months. When the rate rises, the interest charged each month goes up, which means less of your fixed instalment reaches the principal. To keep the instalment steady, many banks respond by extending the tenure rather than raising the monthly outgo. The result is that you pay for more months, and your amortization schedule stretches further into the future. When the rate falls, the reverse happens and the tenure can shorten. Keeping an eye on these changes, and asking your bank whether a revision has altered your instalment or your tenure, helps you stay in control rather than being surprised years later.

A sensible habit is to review your loan statement once or twice a year and rebuild the schedule with your current rate. This tells you how much interest you have actually paid, how much principal remains, and whether an extra prepayment would meaningfully shorten the road ahead. Treating the schedule as a living document, rather than a one-time calculation at sanction, is the single most useful discipline a borrower can adopt.

FAQs

How do I calculate a loan amortization schedule?
First calculate the EMI, then for each month compute interest as balance times the monthly rate, subtract it from the EMI to get principal repaid, and reduce the balance. Repeat until the balance is zero.

Why is most of my early EMI going to interest?
Because interest is charged on the outstanding balance, which is highest at the start. As you repay principal and the balance falls, the interest portion shrinks and the principal portion grows.

Does prepayment help more in the early years?
Yes. Early EMIs are interest-heavy, so prepaying early removes principal that would otherwise attract years of interest, saving the most money. Later prepayment saves far less.

How does the RBI repo rate affect my amortization?
Most Indian home loans are floating and linked to the repo rate plus a spread. When the repo rate changes, your bank resets the rate, often adjusting the tenure, which changes your amortization schedule.

Can I claim tax benefits based on my amortization schedule?
Yes. The schedule shows yearly interest, which supports the Section 24(b) deduction of up to ₹2 lakh on home loan interest, while principal repaid can count towards Section 80C.