The EMI Formula (Reducing Balance Method)
All banks and NBFCs in India use the reducing balance method (also called the diminishing balance method) to calculate EMI. The formula is:
Where:
P = Principal (loan amount)
r = Monthly interest rate = Annual rate ÷ 12 ÷ 100
n = Loan tenure in months
Worked Example — ₹30 Lakh Home Loan at 8.5% for 20 Years
Let us apply the formula step by step:
- P = ₹30,00,000
- Annual rate = 8.5%, so r = 8.5 ÷ 12 ÷ 100 = 0.007083
- n = 20 years × 12 = 240 months
EMI = [30,00,000 × 0.007083 × (1.007083)^240] ÷ [(1.007083)^240 − 1]
(1.007083)^240 = approximately 5.237
EMI = [30,00,000 × 0.007083 × 5.237] ÷ [5.237 − 1]
= [1,11,428] ÷ [4.237]
= ₹26,035 per month
Total amount paid over 20 years: ₹26,035 × 240 = ₹62,48,400
Total interest paid: ₹62,48,400 − ₹30,00,000 = ₹32,48,400
You pay back more than double the loan amount in interest over 20 years. This is why home loan tenure matters enormously.
Why Early EMIs Are Mostly Interest
Each EMI contains two parts: interest and principal repayment. The split changes every month. Here is the amortisation schedule for the first and last few months of the above loan:
| Month | EMI | Interest | Principal | Balance |
|---|---|---|---|---|
| 1 | ₹26,035 | ₹21,250 | ₹4,785 | ₹29,95,215 |
| 2 | ₹26,035 | ₹21,216 | ₹4,819 | ₹29,90,396 |
| 3 | ₹26,035 | ₹21,182 | ₹4,853 | ₹29,85,543 |
| 12 | ₹26,035 | ₹20,905 | ₹5,130 | ₹29,49,910 |
| 60 | ₹26,035 | ₹19,384 | ₹6,651 | ₹27,34,010 |
| 120 | ₹26,035 | ₹16,051 | ₹9,984 | ₹22,66,173 |
| 180 | ₹26,035 | ₹11,101 | ₹14,934 | ₹15,66,130 |
| 230 | ₹26,035 | ₹2,720 | ₹23,315 | ₹3,60,985 |
| 240 | ₹26,035 | ₹183 | ₹25,852 | ₹0 |
At month 1, ₹21,250 of your ₹26,035 EMI (82%) goes to interest. By month 240, only ₹183 goes to interest. This is why prepayment in early years has a dramatically higher impact — every rupee you prepay reduces the principal that is accumulating the highest interest.
The Extra EMI Trick — Saves ₹7 Lakh and 3.5 Years
If instead of 12 EMIs per year, you pay 13 (one extra — perhaps from a bonus), here is what happens on the same ₹30L loan:
- Normal schedule: 240 months, total interest ₹32,48,400
- With 1 extra EMI/year: approximately 198 months (16.5 years), total interest ~₹25,30,000
- Saved: ~3.5 years and ₹7.18 lakh
💡 Best Prepayment Strategy
If you receive an annual bonus, use it to prepay the home loan principal. Prepaying in the first 5 years has the highest impact because that is when the interest component is largest. A ₹1 lakh prepayment in year 2 saves more total interest than the same ₹1 lakh prepayment in year 15.
Flat Rate vs Reducing Balance — The Hidden Trap
Some lenders (particularly personal loan apps and certain NBFCs) quote EMI at a "flat rate". This looks cheaper but is significantly more expensive.
- Flat rate: Interest calculated on original principal for entire tenure. A ₹1L loan at 10% flat for 2 years = ₹10,000 interest per year = ₹20,000 total interest.
- Reducing balance: Same loan at 10% reducing balance = ~₹11,600 total interest (because principal reduces each month).
The problem: lenders often quote a lower flat rate to make it seem cheaper. 10% flat ≈ 18.5% reducing balance. Always convert to reducing balance before comparing offers.
⚠️ Watch Out
Many personal loan apps and small finance companies quote "flat rates". If a loan offer sounds too good compared to bank rates, check whether it is flat or reducing balance. Convert it before signing anything.
How to Reduce Total Interest on Your Loan
- Increase EMI when income grows — Even increasing EMI by ₹2,000/month reduces tenure significantly on long loans.
- Prepay whenever possible — Lump sum from bonus, tax refund, or maturity proceeds. Prepay in early years for maximum impact.
- Shorter tenure from the start — A 15-year loan vs 20-year loan saves enormous interest despite higher monthly EMI.
- Negotiate the interest rate — On floating rate home loans, you can request a rate reduction from your bank when repo rates fall. Many people do not do this and overpay for years.
- Balance transfer — If another bank offers significantly lower rates (0.5%+ difference), a balance transfer can save substantial interest over a long loan.
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Use EMI Calculator →How We Research and Update This Guide
We cross-check formulas, slabs, and examples against published government, regulator, lender, and scheme documentation before updating the page.
- Official government notifications, tax guidance, and scheme rules are checked before formulas or explanatory text are updated.
- Worked examples are recalculated manually and matched against the on-page tool where relevant.
- Whenever rules change, the page date and examples should be revised together to avoid stale guidance.
Frequently Asked Questions — EMI Calculation
EMI = [P × r × (1+r)^n] / [(1+r)^n − 1], where P = Principal loan amount, r = Monthly interest rate (Annual rate ÷ 12 ÷ 100), n = Total number of monthly instalments. This is the reducing balance formula used by all banks and NBFCs in India for home loans, personal loans, and car loans.
This is a natural result of the reducing balance method. In the early months, your outstanding principal is highest, so the interest component (calculated on remaining principal) is large. As you pay EMIs, the principal reduces, and so does the interest component. By the last few years of a loan, most of each EMI goes to principal repayment.
Yes — significantly. On a ₹30 lakh home loan at 8.5% for 20 years, paying one extra EMI per year (i.e., 13 EMIs instead of 12 annually) reduces the loan tenure by approximately 3.5 years and saves over ₹7 lakh in interest. The exact savings depend on loan amount, rate, and tenure.
Flat rate calculates interest on the full original principal throughout the loan — making it appear cheaper but actually costing more. Reducing balance (used by all regulated banks) calculates interest on the remaining outstanding principal, which decreases with each EMI. A 10% flat rate is equivalent to roughly 18-19% reducing balance — a critical difference when comparing loan offers.
Prepayment reduces your outstanding principal directly. You can either reduce EMI while keeping tenure the same, or keep the same EMI and reduce tenure. Reducing tenure saves more interest. Most banks allow partial prepayment on floating rate home loans without penalty. Fixed rate loans may have prepayment charges.