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How to Calculate Home Loan EMI and Reduce Total Interest
By Chirag
An EMI looks like one fixed number, but the split inside it changes every month. Once you see that split for a real loan, it becomes clear which levers cut your total interest and which ones only make the monthly figure feel smaller. All the numbers below use the same loan: ₹40,00,000 at 8.5% a year for 20 years.
The EMI formula, worked through
EMI = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)
- P = ₹40,00,000 (the amount borrowed)
- r = 8.5 ÷ 12 ÷ 100 = 0.0070833 (the monthly rate)
- n = 20 × 12 = 240 (the number of monthly instalments)
That gives an EMI of ₹34,713. Over 240 months you pay ₹83,31,103 in total. Of that, ₹43,31,103 is interest, more than the amount you borrowed.
Where the first EMIs actually go
Interest each month is charged on the balance still outstanding, and the balance is largest at the start.
- Month 1: interest = 40,00,000 × 0.0070833 = ₹28,333. Only ₹6,380 of the ₹34,713 reduces the loan.
- After 5 years (60 EMIs, ₹20,82,776 paid in total), the outstanding balance is still ₹35,25,087. Only ₹4,74,913 of the principal is gone; ₹16,07,863 went to interest.
This front-loading is why the timing of anything you do to the loan matters so much.
Lever 1: a shorter tenure
The same loan over 15 years:
| Tenure | EMI | Total interest |
|---|---|---|
| 20 years | ₹34,713 | ₹43,31,103 |
| 15 years | ₹39,390 | ₹30,90,125 |
Paying ₹4,677 more each month saves ₹12,40,978 in interest. If the higher EMI fits your budget comfortably, this is the biggest single lever you control at signing time. It works the other way too: stretching the same loan to 30 years brings the EMI down to ₹30,757, only ₹3,956 less, but total interest climbs to ₹70,72,354, which is ₹27,41,251 more than the 20-year loan.
Lever 2: the interest rate
A half-point difference looks small on a rate card:
| Rate (20 years) | EMI | Total interest |
|---|---|---|
| 8.0% | ₹33,458 | ₹40,29,825 |
| 8.5% | ₹34,713 | ₹43,31,103 |
| 9.0% | ₹35,989 | ₹46,37,369 |
Between 8.5% and 9.0%, the EMI moves by ₹1,276, but total interest moves by ₹3,06,266. That's why comparing a few lenders, or asking your current lender to move you to a lower rate, is worth an afternoon's paperwork.
Lever 3: prepayments, and which option to pick
A small extra amount every month. Adding ₹5,000 to every EMI from the first month closes the loan in 178 months (14 years 10 months) instead of 240, and saves ₹12,98,954 in interest.
A one-time lump sum. Say you pay ₹3,00,000 extra right after the 36th EMI. Lenders usually ask what you want to do next:
| After the ₹3 lakh prepayment | Result | Interest saved |
|---|---|---|
| Keep the EMI, shorten the tenure | Loan ends at month 208 (17 years 4 months) | ₹8,30,135 |
| Keep the tenure, lower the EMI | EMI drops to ₹31,928 | ₹2,68,115 |
The same ₹3 lakh saves about three times as much if you keep paying the old EMI. Lowering the EMI helps monthly cash flow, but the balance then shrinks more slowly for the rest of the loan.
Charges and rate resets on floating-rate loans
RBI rules don't allow lenders to charge foreclosure or prepayment penalties on floating-rate loans taken by individuals for non-business purposes, which covers most home loans. Fixed-rate loans can carry a charge, so check your sanction letter before prepaying one.
When a floating rate goes up, a lender may extend the tenure instead of raising the EMI. Your monthly payment stays put, but total interest climbs quietly, sometimes by a lot. RBI's 2023 rules on resetting floating rates require lenders to tell you about the change and let you choose a higher EMI, a longer tenure or a mix of the two. A switch to a fixed rate at the reset is no longer something you can count on: since 1 October 2025 lenders offer it only at their own option, under their board-approved policy (RBI amendment of 29 September 2025), so check your sanction letter. Picking the higher EMI keeps you close to your original payoff date.
A note on tax
FY 2026-27 is the first tax year under the new Income-tax Act, 2025, and the position is the same as before. The deduction for home-loan interest on a self-occupied house (up to ₹2 lakh a year, now in section 22(2) of the new Act in place of section 24(b)) and the principal deduction within the ₹1.5 lakh investment limit are available only under the old tax regime. The new regime, which is the default, doesn't allow them for a self-occupied home, and Budget 2026 left the tax rates for the year unchanged (Finance Bill 2026 memorandum). These rules change with budgets, so check the current year's position before counting a tax saving in your plan.
Running these numbers on your own loan
- For a single EMI and total interest figure, use the EMI Calculator.
- To test a monthly prepayment or compare three interest rates side by side, use the Advanced Home Loan Calculator. It also shows a year-by-year or month-by-month schedule you can download as CSV.
- To compare two actual loan offers with different amounts, rates, or tenures, run each one through the EMI Calculator and compare the total interest, not just the EMI.
For why interest charged on a falling balance behaves so differently from a flat percentage, see simple vs compound interest.
Related guides
- Simple vs Compound Interest: Worked in Rupees Over 30 Years · ₹1,00,000 at 7% under simple interest and yearly, quarterly and monthly compounding over 1 to 30 years, what an effective annual rate is, and why a 10% "flat" loan rate costs as much as 17.92% on a reducing balance.
- Why Your In-Hand Salary Is Lower Than Your CTC · A line-by-line breakdown of an ₹8 lakh CTC showing where the money goes (employer PF, your own PF, professional tax, and TDS), plus the PF wage-ceiling detail that can change your in-hand pay by thousands a month.
- ROI, Payback and Depreciation: One Purchase, Worked Through All Three · A ₹2,40,000 coffee machine run through payback period, ROI, annualized ROI and straight-line depreciation, why the annualized figure understates a machine that pays back monthly (25.9% vs 74.3%), and what depreciation does to reported profit.