You're about to sign a 20-year home loan. The bank says your EMI is ₹45,000. You nod, but you have no idea how they got that number — or whether it's correct. Banks don't explain the formula. They hand you a number and expect you to trust it.
Here's the math they don't teach you in school but should.
The EMI Formula
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 months (years × 12)
This is the reducing balance method — the standard method used by all Indian banks. Each month, you pay interest on the remaining balance, not the original loan amount.
Step-by-Step: ₹25 Lakh Home Loan at 8.5% for 20 Years
- P = 25,00,000
- r = 8.5 ÷ 12 ÷ 100 = 0.007083
- n = 20 × 12 = 240 months
- (1+r)ⁿ = (1.007083)²⁴⁰ = 5.4276
- EMI = 25,00,000 × 0.007083 × 5.4276 ÷ (5.4276 − 1)
- EMI = ₹21,799/month
Total paid: ₹21,799 × 240 = ₹52,31,760 Total interest: ₹52,31,760 − ₹25,00,000 = ₹27,31,760
You pay more in interest (₹27.3 lakh) than the original loan (₹25 lakh). That's the reality of long-term borrowing.
Use our Loan EMI Calculator to compute EMI instantly for any loan amount, rate, and tenure.
How EMI Splits: Principal vs Interest
In the first month of the loan above:
| Component | Calculation | Amount | |-----------|------------|--------| | Interest | ₹25,00,000 × 0.007083 | ₹17,708 | | Principal | ₹21,799 − ₹17,708 | ₹4,091 |
81% of your first EMI goes to interest. Only 19% reduces your actual loan.
The Amortization Shift
Over time, the split reverses:
| Year | EMI (Annual) | Interest Portion | Principal Portion | Interest % | |------|-------------|-----------------|-------------------|-----------| | 1 | ₹2,61,588 | ₹2,10,728 | ₹50,860 | 80.6% | | 5 | ₹2,61,588 | ₹1,86,432 | ₹75,156 | 71.3% | | 10 | ₹2,61,588 | ₹1,42,980 | ₹1,18,608 | 54.7% | | 15 | ₹2,61,588 | ₹85,424 | ₹1,76,164 | 32.7% | | 20 | ₹2,61,588 | ₹10,428 | ₹2,51,160 | 4.0% |
The Trench Truth: The bank front-loads the interest. In the first 5 years of a 20-year loan, you pay 80% of the total interest but only reduce the principal by 15%. This is why prepayment in the early years saves you the most money. A ₹5 lakh prepayment in Year 1 can save you ₹15 lakh in total interest. The same prepayment in Year 15 saves barely ₹2 lakh.
Different Loan Types
Home Loan
- Typical rate: 8-9.5% (India, 2024)
- Tenure: 15-30 years
- Tax benefit: Section 80C (principal up to ₹1.5L) + Section 24(b) (interest up to ₹2L)
- Collateral: The property itself
Car Loan
- Typical rate: 8.5-12%
- Tenure: 3-7 years
- Tax benefit: None (unless car used for business)
- Depreciation: Car loses 15-20% value in Year 1 — you may owe more than the car is worth
Personal Loan
- Typical rate: 10-24%
- Tenure: 1-5 years
- Tax benefit: None
- No collateral — which is why rates are so high
Education Loan
- Typical rate: 8-12% (subsidized for lower income)
- Tenure: 5-15 years (moratorium during study period)
- Tax benefit: Section 80E (entire interest amount, no limit)
- Collateral: Required above ₹7.5 lakh
The Impact of Interest Rate Changes
Even a 0.5% rate change dramatically affects your total payment:
| Rate | EMI (₹25L, 20yr) | Total Interest | Difference | |------|-------------------|---------------|------------| | 8.0% | ₹20,911 | ₹25,18,640 | Baseline | | 8.5% | ₹21,799 | ₹27,31,760 | +₹2.13L | | 9.0% | ₹22,497 | ₹28,99,280 | +₹3.81L | | 9.5% | ₹23,207 | ₹31,69,680 | +₹6.51L |
A 1.5% rate increase costs you ₹6.5 lakh extra in interest. This is why negotiating your rate matters more than negotiating the car price.
Prepayment: How to Save Lakhs
Making a one-time prepayment reduces the principal, which reduces future interest on the remaining balance.
Example: ₹5 lakh prepayment after Year 2
| Scenario | Total Interest | Interest Saved | |----------|---------------|---------------| | No prepayment | ₹27,31,760 | — | | ₹5L prepayment, reduce tenure | ₹20,89,440 | ₹6,42,320 | | ₹5L prepayment, reduce EMI | ₹22,15,680 | ₹5,16,080 |
Reducing tenure saves more than reducing EMI because you're eliminating high-interest months at the end of the loan.
Frequently Asked Questions
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