Overview
Amortization is the process of repaying a loan through a series of fixed periodic payments, where each payment covers both interest owed and a portion of the principal. The key feature: the payment amount stays constant, but the split between interest and principal shifts with every instalment. Early payments are heavily weighted toward interest; later payments shift toward principal repayment.
Understanding this split matters because it tells you exactly how much of your money is building equity versus paying the lender's cost of credit — and it shows you precisely where a prepayment delivers the most savings.
What You Need
Before building an amortization schedule, gather three numbers:
- Loan principal (P): The amount borrowed — for example, Rs 50,00,000.
- Annual interest rate: The reducing-balance rate quoted by your lender — for example, 8.5% per annum.
- Tenure in months (n): Total number of EMIs — for example, 20 years = 240 months.
Step 1: Calculate the Monthly Interest Rate
Annual rates must be converted to a monthly rate before applying the EMI formula.
Formula:
r = Annual Rate / 12 / 100
Example — 8.5% annual rate:
r = 8.5 / 12 / 100 = 0.007083
This means each rupee of outstanding balance costs Rs 0.007083 in interest every month.
Step 2: Calculate the EMI
The standard reducing-balance EMI formula is:
EMI = P × r × (1 + r)^n / [(1 + r)^n − 1]
Example — Rs 50,00,000 at 8.5% for 240 months:
(1 + 0.007083)^240 = 5.3175
EMI = 50,00,000 × 0.007083 × 5.3175 / (5.3175 − 1)
= 50,00,000 × 0.007083 × 5.3175 / 4.3175
= Rs 43,391
Every month, Rs 43,391 leaves your account. The proportion going to interest versus principal is what changes.
Use the loan-amortization-calculator-india to get this figure instantly without manual computation, and to generate the full schedule automatically.
Step 3: Build Month 1 of the Schedule
With principal, rate, and EMI in hand, month 1 is straightforward:
| Field | Calculation | Amount |
|---|---|---|
| Opening balance | — | Rs 50,00,000 |
| Interest | 50,00,000 × 0.007083 | Rs 35,417 |
| Principal | 43,391 − 35,417 | Rs 7,974 |
| Closing balance | 50,00,000 − 7,974 | Rs 49,92,026 |
In month 1, only Rs 7,974 of your Rs 43,391 payment reduces your debt. Rs 35,417 — over 81% — goes to interest.
Step 4: Build Month 2 and Continue the Pattern
Month 2 starts from the closing balance of month 1:
| Field | Calculation | Amount |
|---|---|---|
| Opening balance | — | Rs 49,92,026 |
| Interest | 49,92,026 × 0.007083 | Rs 35,360 |
| Principal | 43,391 − 35,360 | Rs 8,031 |
| Closing balance | 49,92,026 − 8,031 | Rs 49,83,995 |
The interest dropped by Rs 57 and the principal repaid increased by Rs 57. This shift is small each month but compounds over time. Repeat this for all 240 rows and you have a complete amortization schedule.
Step 5: Read the Full Schedule
Manually building 240 rows is tedious. The loan-amortization-calculator-india generates the complete schedule in seconds and lets you download it.
To see how dramatically the split changes over time, look at month 100 of the same Rs 50,00,000 loan:
| Metric | Month 1 | Month 100 | Month 200 |
|---|---|---|---|
| Opening balance | Rs 50,00,000 | Rs 41,80,000 | Rs 22,50,000 |
| Interest portion | Rs 35,417 | Rs 29,600 | Rs 15,940 |
| Principal portion | Rs 7,974 | Rs 13,791 | Rs 27,451 |
By month 200 of 240, more than 63% of each EMI is retiring principal. This is why the final years of a loan "feel faster" — you are actually making meaningful progress on the debt.
Step 6: Model Prepayments
A prepayment is any lump-sum payment made over and above the regular EMI. Because it directly reduces the outstanding principal, every future month's interest is recalculated on a lower base.
Example: A Rs 1,00,000 prepayment at month 12 on the same Rs 50,00,000 loan.
- Outstanding balance at month 12 before prepayment: approximately Rs 49,04,000
- After prepayment: Rs 48,04,000
- All future interest is now calculated on Rs 48,04,000 instead of Rs 49,04,000
- Estimated interest saving: approximately Rs 2.8 lakh over the remaining tenure
- Estimated tenure reduction: approximately 18 months
Use the loan-prepayment-calculator-india to model exact savings for your loan amount, rate, and prepayment timing. Earlier prepayments save more because the interest clock runs longest on any amount prepaid early.
Why Amortization Front-Loads Interest
The front-loading of interest is not arbitrary — it is a mathematical consequence of charging interest on the outstanding balance. When the balance is at its maximum (month 1), the largest possible interest amount is deducted first, leaving the smallest slice for principal reduction. As the balance shrinks, interest shrinks, and the principal portion grows.
This has a practical implication: refinancing or making prepayments early in the loan tenure delivers the biggest savings. A prepayment at month 12 saves more than the same prepayment at month 120, because month-12 prepayment eliminates interest that would have compounded over 228 remaining months, versus only 120 months.
It also explains why borrowers who refinance a 10-year-old home loan to a lower rate are sometimes disappointed — a large share of the interest on that loan was already paid in the first decade. The remaining balance is smaller, so the absolute saving from a lower rate is reduced.
EMI vs Principal-Only vs Interest-Only Payments
Standard Indian home loans use the reducing-balance EMI method described above — the same fixed payment every month, with a shifting split. Two alternative structures sometimes appear in specialised products:
- Interest-only payments: The borrower pays only interest each month; the full principal is due at maturity. Common in some overdraft products and construction-phase loans. No amortization occurs — the outstanding balance stays unchanged.
- Principal-only payments: Rare in retail lending. If structured this way, each payment reduces the balance by a fixed principal amount, while the interest portion decreases every month. Total outflow is higher early but falls over time.
For virtually all retail home, car, and personal loans in India, you are on the standard EMI amortization schedule described in this guide.
Key Terms
- Amortization — The process of paying off a debt through scheduled periodic payments that cover both interest and principal.
- EMI — Equated Monthly Instalment; the fixed monthly payment amount calculated using the reducing-balance formula.
- Principal — The original loan amount borrowed, or the outstanding balance yet to be repaid at any point in time.
- Prepayment — A lump-sum payment made in addition to regular EMIs, which directly reduces the outstanding principal and future interest.
Related Tools
- Loan Amortization Calculator — Generate a complete month-by-month amortization schedule for any loan.
- Home Loan EMI Calculator — Calculate EMI, total interest, and total payment for home loans with a visual breakdown.
- Loan Prepayment Calculator — Model interest savings and tenure reduction from one-time or recurring prepayments.