Best Way to Calculate Bank Loan EMI: Reducing Balance vs Flat Rate
By Pradipta Ray · Published
How do commercial banks actually compute your monthly EMI? While lenders often quote headline rates or flat rates, every retail loan in India amortizes on a reducing balance basis. Here is the exact mathematical mechanism.
When you take out a loan from an Indian commercial bank, your monthly instalment is calculated using compound interest amortization. Because interest is charged only on the unpaid principal balance at the end of each month, your payment structure changes continuously beneath the hood.
Direct Answer: Indian banks calculate EMI using the annuity formula: EMI = [P × r × (1 + r)^n] / [(1 + r)^n - 1]. On a ₹10,00,000 loan at 9.00% p.a. for 5 years (60 months), the monthly EMI is ₹20,758, resulting in total interest of ₹2,45,501.
Step-by-Step Mathematical Walkthrough (₹10 Lakh at 9% for 5 Years)
| Variable | Description | Value in Example | Calculation |
|---|---|---|---|
| P (Principal) | Sanctioned loan amount | ₹10,00,000 | Base borrowed sum |
| r (Monthly Rate) | Annual rate divided by 12 months and 100 | 0.0075 | 9.00 ÷ 1200 = 0.0075 |
| n (Tenure) | Total number of monthly instalments | 60 months | 5 years × 12 months |
| (1 + r)^n | Compounding factor | 1.56568 | (1.0075)^60 |
| Calculated EMI | P × r × [(1 + r)^n] ÷ [(1 + r)^n - 1] | ₹20,758 per month | [10,00,000 × 0.0075 × 1.56568] ÷ 0.56568 |
The Flat Rate Trap: Why Dealers Quote Flat Rates
Automobile dealers and consumer durable NBFCs frequently quote '5.5% flat interest' to make loans appear cheap. In a flat loan, interest is computed on the entire original ₹10 Lakh principal for all 5 years, costing ₹2,75,000 in interest. In a reducing loan at 5.5%, interest would only be ₹1,46,000! A 5.5% flat loan is actually equal to a 10.1% reducing balance loan.
Key Checkpoints for Every Borrower
Demand the Key Fact Statement (KFS) mandated by RBI, which explicitly discloses the Annual Percentage Rate (APR) including all fees.
Check amortization schedule: Ensure the majority of your payment starts shifting from interest to principal by the midpoint of the loan.
Always verify whether the benchmark is linked to RBI Repo Rate (EBLR/RLLR) for floating loans.
Frequently asked questions
What formula do Indian banks use to calculate loan EMI?
Why is a flat interest rate misleading?
Why does my bank's sanctioned EMI differ by a few rupees from online calculators?
Calculators for this
Related reading
How Indian lenders work out your monthly instalment, why the interest portion shrinks every month, and what actually changes the number.
The reducing-balance EMI formula Indian lenders use, what each symbol means, how to compute it yourself, and how to handle the 0% case.
Why a flat 10% and a reducing-balance 10% are not the same loan, how much more the flat structure costs, and where you meet it in India.
Authoritative Sources
- Reserve Bank of India Master Circular on Loans and Advances· verified 1 August 2026
- Indian Banks' Association Code of Banking Practice· verified 1 July 2026