A loan offer usually comes with one headline number — the EMI — and little explanation of how it was calculated. It's not complicated once you see the formula, and understanding it explains a few things that otherwise feel unintuitive, like why a longer tenure can quietly cost you far more even at the same interest rate.
The formula
EMI is calculated as:
EMI = P × r × (1 + r)ⁿ / ((1 + r)ⁿ - 1)
Where P is the loan principal, r is the monthly interest rate (your annual rate divided by 12, then by 100 to convert from a percentage), and n is the number of monthly installments. This produces a single fixed payment that, if made every month for the full tenure, exactly pays off both the principal and all the interest — no more, no less.
The one exception: at a 0% interest rate, the formula above breaks down (you'd be dividing by zero), so it simplifies to just the principal divided evenly by the number of months — no interest component to calculate at all.
Why early payments feel like they barely touch the principal
Your EMI amount is fixed for the life of the loan, but the split between "interest" and "principal" inside each payment isn't. Early on, most of your loan balance is still outstanding, so interest — which is calculated on the remaining balance — makes up the bulk of each payment. As the balance shrinks over time, less of each fixed EMI goes to interest and more goes to actually paying down the principal. This is normal and not a sign of a bad loan; it's just how amortization works on any fixed-installment loan.
The lever that matters most: tenure
A longer tenure lowers your monthly EMI — which is why it's the easiest way for a lender to make a loan look more "affordable" — but it also means you're paying interest for more months, which increases the total interest paid over the life of the loan, sometimes dramatically. Two loans at the identical interest rate and principal can have wildly different total costs purely based on tenure. Total interest paid (EMI × number of months, minus the original principal) is the number worth comparing across offers, not just the monthly figure.
Using the tool
Our EMI Calculator takes your loan amount, annual interest rate, and tenure in months, and returns your monthly EMI, total interest, and total payment over the full loan — so you can see the tenure trade-off directly instead of just the monthly number in isolation.
Try it here: EMI Calculator.