May 2026  |  A Complete Guide with Example

Introduction

When you take out a loan whether for a home, car, or personal need the bank doesn’t just hand you money and wait. It charges interest, and that interest is collected via monthly EMI (Equated Monthly Instalment) payments. But not all interest calculations are the same.

There are two dominant methods lenders use to calculate interest on a loan:

• Flat Rate Method simple but more expensive
• Reducing Balance Method fairer and widely used by banks

Understanding the difference can save you thousands of rupees. Let’s break both down with clear examples.

Part 1: The Flat Rate Method

What Is the Flat Rate Method?

In the Flat Rate Method, interest is calculated on the original principal for the entire loan tenure regardless of how much you have already repaid. This means even if you’ve paid back 80% of the loan, you still pay interest as if 100% is outstanding.

Formula

Total Interest  =  P × r × n

EMI  =  (P + Total Interest) ÷ n

Where: P = Principal | r = Annual interest rate | n = Tenure in years

Example 1 Flat Rate

Step 1: Calculate Total Interest

Total Interest = 2,00,000 × 10% × 2 = Rs. 40,000

Step 2: Calculate EMI

EMI = (2,00,000 + 40,000) ÷ 24 = 2,40,000 ÷ 24 = Rs. 10,000 per month

Amortisation Schedule (Flat Rate)

Key observation: Notice the interest column stays FIXED at Rs. 1,667 every single month. Even in month 18 when you’ve paid back Rs. 1,58,327, you still pay interest on the original Rs. 2,00,000. This is the core limitation of the flat rate method.

Total Amount Paid: 24 × Rs. 10,000 = Rs. 2,40,000  |  Total Interest: Rs. 40,000

Part 2: The Reducing Balance Method

What Is the Reducing Balance Method?

In the Reducing Balance Method (also called the Diminishing Balance Method), interest is calculated only on the outstanding loan balance after each EMI payment. As you repay principal, your interest liability shrinks every month.

This method is used by banks for home loans, car loans, and most personal loans in India.

Formulas

EMI  =  [P × i × (1+i)ⁿ] ÷ [(1+i)ⁿ − 1]

Interest in kᵗʰ EMI  =  E × [(1+i)^(n−k+1) − 1] ÷ (1+i)^(n−k+1)

Principal in kᵗʰ EMI  =  EMI − Interestₖ

Where: P = Principal | i = Monthly interest rate (annual rate ÷ 12) | n = Total months | k = Instalment number

Example 2 Reducing Balance

Step 1: Calculate EMI

i = 0.10 ÷ 12 = 0.008333

(1+i)ⁿ = (1.008333)²⁴ = 1.2204

EMI = [2,00,000 × 0.008333 × 1.2204] ÷ [1.2204 − 1]

EMI = [2033.4] ÷ [0.2204] = Rs. 9,226 per month (approx.)

Amortisation Schedule (Reducing Balance)

Key observation: Interest drops from Rs. 1,667 in month 1 to just Rs. 76 in the final month. This is because you’re paying interest only on the remaining balance, not the original loan. Principal repayment grows every month.

Total Amount Paid: 24 × Rs. 9,226 = Rs. 2,21,424  |  Total Interest: Rs. 21,424

Side-by-Side Comparison

Same loan (Rs. 2,00,000 at 10% for 2 years) two very different outcomes:

Key Takeaways for Borrowers

• Always ask your lender: “Is this flat rate or reducing balance?” before signing.
• A flat rate of 7% is roughly equivalent to 12 to 13% on a reducing balance basis.
• Banks and NBFCs in India use reducing balance for home, car, and most personal loans.
• Some consumer durable and jewellery loans still use the flat rate read the fine print.
• Use the formula n × E − P to quickly calculate total interest on any loan.
• Prepaying your loan in a reducing balance setup saves disproportionately more interest.

Final Word

The math of EMI is simple once you know the method. The reducing balance approach is always more borrower-friendly because you should only pay interest on what you actually owe, not what you originally borrowed. Be an informed borrower: compare, calculate, and choose wisely.

– Happy Borrowing!