How EMI is calculated, step by step
The formula behind every EMI, and why early instalments are mostly interest.
EMI stands for Equated Monthly Instalment — the fixed amount you pay every month for the life of a loan. The amount never changes, but what it’s made of does: every EMI is split between interest (what you’re paying to borrow) and principal (what actually reduces your debt), and that split shifts completely over the loan’s life.
Almost every EMI in India — home, personal, car, education — uses the same reducing-balance formula. Once you understand it, you can sanity-check any loan offer yourself instead of trusting the number a lender hands you.
The reducing-balance formula
The EMI formula has three inputs and one output:
EMI = P × r × (1 + r)n ÷ [(1 + r)n − 1]
| Symbol | Meaning |
|---|---|
| P | Principal — the amount you borrow |
| r | Monthly interest rate — the annual rate divided by 12, then by 100 |
| n | Tenure in months |
A ₹10,00,000 loan at 9% p.a. over 5 years (60 months) works out to an EMI of ₹20,758. Over the full tenure you pay ₹2,45,501 in interest — total repayment of ₹12,45,501 against the ₹10,00,000 you borrowed.
Why early EMIs are mostly interest
Interest is charged on whatever principal is still outstanding — not on the original loan amount. Early on, your outstanding balance is at its highest, so the interest portion of each EMI is at its highest too. As the balance shrinks month by month, less of each EMI goes to interest and more goes to principal, even though the EMI itself never changes.
| Month | Interest | Principal |
|---|---|---|
| Month 1 | ₹7,500 (36% of the EMI) | ₹13,258 (64% of the EMI) |
| Month 60 (last) | ₹155 (under 1% of the EMI) | ₹20,604 (over 99% of the EMI) |
This is also why prepaying a loan early saves so much more interest than prepaying the same amount near the end — early prepayments cut principal while the interest meter is still running hottest.
Flat rate vs. reducing balance
Some lenders — car dealerships and consumer-durable financing are the most common culprits — quote a flat rate instead of a reducing-balance rate. A flat rate is calculated on the original principal for the entire tenure, ignoring the fact that your balance is shrinking every month. That makes it look much lower than it actually is.
A flat rate of 5% can work out equivalent to a reducing-balance rate of roughly 9–10% over a typical 3–5 year tenure — the exact gap depends on tenure, but it’s never small. Always ask for the reducing-balance rate (or the APR) before comparing two loan offers on rate alone.
What actually changes your EMI
Three inputs, and they don’t all move your EMI the same way:
- Principal — EMI scales roughly linearly with how much you borrow
- Rate — a higher rate raises the EMI and disproportionately raises total interest paid
- Tenure— a longer tenure lowers the EMI, but increases total interest paid — you’re trading a smaller monthly number for a larger lifetime one
Calculate the monthly instalment for any loan amount, rate and tenure.
This same formula and reducing-balance logic is exactly what powers the Personal Loan, Car Loan and Education Loan calculators — the math doesn’t change with the label on the loan. If you’re not sure how much you could even qualify for first, the Loan Eligibility Calculator is the place to start.
All figures are indicative and for educational purposes only — not financial advice.
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