Why does my bank's EMI differ slightly from the formula result?

Small differences usually come from rounding conventions the lender uses internally, processing fees or insurance folded into the stated EMI, or the rate being applied on a slightly different day-count basis. The formula gives the pure principal-and-interest figure; compare it against your loan's amortisation schedule for the exact match.

Does prepaying a loan reduce my EMI or shorten the tenure?

Most lenders let you choose. Reducing the tenure while keeping the EMI the same saves more total interest, because you spend less time paying interest on the outstanding balance. Reducing the EMI while keeping the tenure the same gives you lower monthly payments but saves less overall.

Is EMI calculated on the full original loan amount the whole way through?

No — interest each month is calculated only on the outstanding (reducing) balance, not the original principal. That's exactly why early EMIs are interest-heavy: the outstanding balance is at its largest then, and it shrinks a little more with every payment.

If I double my EMI, does my loan finish in half the time?

No, it finishes in less than half the time. Because interest is charged on a shrinking balance, extra payments go disproportionately toward principal, which snowballs — the last few months of a loan clear very quickly once the balance is small, so a higher EMI shortens the tenure by more than a proportional amount.

How EMI Is Actually Calculated, With a Worked Example

The formula banks use, worked by hand on a real loan so every number is checked.

Updated 12 September 2026

What EMI actually is

An EMI (Equated Monthly Instalment) is a fixed monthly payment that repays a loan over a set number of months. Every instalment is the same size, but the mix inside it changes: early payments are mostly interest with a little principal, and later payments flip to mostly principal with a little interest. The total you owe still hits zero exactly on the last instalment — that balancing act is what the EMI formula is solving for.

The formula, term by term

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

P is the principal — the amount you actually borrowed. r is the monthly interest rate, which is the annual rate divided by 12 and then by 100 to turn a percentage into a decimal (a 9% annual rate becomes r = 0.0075). n is the total number of monthly instalments — a 5-year loan is n = 60, not 5.

The (1 + r)ⁿ term is doing the actual compounding: it's how much ₹1 of principal would grow to after n months at rate r. The formula uses it twice — once to project the whole loan forward, once to spread that growth evenly across every instalment — which is why the same term appears in both the numerator and denominator.

A full worked example

Take a loan of ₹5,00,000 at 9% annual interest over 5 years.

First, convert the annual rate to a monthly one: r = 9 ÷ 12 ÷ 100 = 0.0075. Then convert the term to months: n = 5 × 12 = 60.

(1.0075)⁶⁰ works out to roughly 1.5657. Plugging everything in: EMI = 5,00,000 × 0.0075 × 1.5657 ÷ (1.5657 − 1) = 5,871 ÷ 0.5657 ≈ ₹10,380 a month.

Over 60 months that's a total repayment of about ₹6,22,800 — meaning roughly ₹1,22,800 of the total is interest, on top of the ₹5,00,000 principal. (Run the same numbers through the Loan EMI Calculator to see this instantly instead of by hand, and to try your own principal, rate and tenure.)

Why a longer tenure can cost more than it looks

Stretching the same ₹5,00,000 loan at 9% over a longer term drops the monthly EMI, which is why longer tenures feel more affordable — but the total interest paid moves in the opposite direction, and not by a small amount:

• 3 years (36 months): EMI ≈ ₹15,890/month, total interest ≈ ₹71,900 • 5 years (60 months): EMI ≈ ₹10,380/month, total interest ≈ ₹1,22,800 • 10 years (120 months): EMI ≈ ₹6,330/month, total interest ≈ ₹2,60,000

Going from 5 years to 10 years roughly halves the EMI, but more than doubles the total interest paid on the exact same loan. Neither figure is 'right' on its own — it depends whether your priority is the smallest monthly outlay or the smallest total cost — but the tenure decision should always be made by looking at both, not the EMI alone.

Frequently asked questions

Why does my bank's EMI differ slightly from the formula result?: Small differences usually come from rounding conventions the lender uses internally, processing fees or insurance folded into the stated EMI, or the rate being applied on a slightly different day-count basis. The formula gives the pure principal-and-interest figure; compare it against your loan's amortisation schedule for the exact match.
Does prepaying a loan reduce my EMI or shorten the tenure?: Most lenders let you choose. Reducing the tenure while keeping the EMI the same saves more total interest, because you spend less time paying interest on the outstanding balance. Reducing the EMI while keeping the tenure the same gives you lower monthly payments but saves less overall.
Is EMI calculated on the full original loan amount the whole way through?: No — interest each month is calculated only on the outstanding (reducing) balance, not the original principal. That's exactly why early EMIs are interest-heavy: the outstanding balance is at its largest then, and it shrinks a little more with every payment.
If I double my EMI, does my loan finish in half the time?: No, it finishes in less than half the time. Because interest is charged on a shrinking balance, extra payments go disproportionately toward principal, which snowballs — the last few months of a loan clear very quickly once the balance is small, so a higher EMI shortens the tenure by more than a proportional amount.