Understanding your loan instalment
Where the EMI figure comes from, why the same instalment costs wildly different amounts, and the four decisions that actually change what you pay.
Last reviewed · 1,579 words
In short
- The EMI is fixed on a fixed-rate loan, but what it is made of changes every month — early instalments are mostly interest.
- Tenure is the most expensive decision. ₹10,00,000 at 9.5% costs about ₹5.5 lakh in interest over ten years and about ₹12.4 lakh over twenty.
- A flat rate is roughly double the reducing-balance rate it is quoted against. Always compare like with like.
- Prepaying early saves far more than prepaying late, and keeping the instalment while shortening the tenure saves more than reducing the instalment.
- The advertised rate is not the cost. Processing fees, insurance sold alongside and prepayment charges all belong in the comparison.
An EMI — equated monthly instalment — is the single amount you pay a lender every month until a loan is cleared. The word doing the work is equated. The payment is level, deliberately, so that a household can budget around it. What is not level is what that payment is doing, and that is where most of the confusion about loans lives.
The formula, and what each part means
The standard EMI on a reducing-balance loan is:
EMI = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1)
Three inputs, and only three:
- P is the principal — the amount actually disbursed to you, not the price of the thing you are buying. If you put down 20% on a house, P is the other 80%.
- r is the monthly interest rate. A lender quotes an annual figure, so divide by twelve and then by a hundred: 9.5% per annum becomes 0.0079166 per month.
- n is the number of monthly instalments. Twenty years is 240, not 20.
The shape of the formula is less forbidding than it looks. The numerator is what one month's interest would be if the whole loan sat there compounding for the full term. The denominator spreads that across the instalments. Everything the formula does is decide how much of each payment goes to interest and how much retires the debt.
A worked example
Take ₹10,00,000 at 9.5% per annum over ten years — the defaults in the calculator above.
- r = 9.5 ÷ 12 ÷ 100 = 0.00791667
- n = 10 × 12 = 120
- (1 + r)ⁿ = 2.5761
Put those in and the EMI is ₹12,940. Over 120 months you pay ₹15,52,771 in total, of which ₹5,52,771 is interest — you repay a bit over one and a half times what you borrowed.
Why the first instalment feels like it did nothing
Interest each month is charged on what you still owe. In month one you owe the whole ₹10,00,000, so the interest is:
₹10,00,000 × 0.00791667 = ₹7,917
Your instalment is ₹12,940. Interest takes ₹7,917 of it, and only ₹5,023 comes off the loan. After a full month of paying, you owe ₹9,94,977.
By the final month the balance is tiny, so almost the entire instalment is principal. The instalment never changed; its composition inverted completely. This is why:
- A loan feels immovable for the first few years and then collapses quickly.
- Selling a house four years into a twenty-year loan leaves a balance far higher than "four twentieths paid off" would suggest.
- A prepayment in year two is worth several times the same rupees in year fifteen — it removes principal that would otherwise have been charged interest for eighteen more years.
The schedule under the calculator shows the first month, the midpoint and the last, which is usually enough to make the pattern obvious.
Tenure is the expensive decision
Lenders sell tenure as affordability, and in cash-flow terms they are right. In total-cost terms it is the most expensive lever on the page. The same ₹10,00,000 at 9.5%:
| Tenure | Monthly EMI | Total interest | Total repaid |
|---|---|---|---|
| 5 years | ₹21,002 | ₹2,60,112 | ₹12,60,112 |
| 10 years | ₹12,940 | ₹5,52,771 | ₹15,52,771 |
| 15 years | ₹10,442 | ₹8,79,604 | ₹18,79,604 |
| 20 years | ₹9,321 | ₹12,37,115 | ₹22,37,115 |
Going from ten years to twenty cuts the monthly figure by ₹3,619 — about 28% — and adds ₹6,84,344 of interest. At twenty years you pay more in interest than you borrowed in the first place.
That is not an argument for always choosing the shortest tenure. A stretched EMI you can actually service beats a tight one that forces you into a credit card at 40% the first time a hospital bill arrives. It is an argument for knowing the price of the comfort, and for shortening the tenure later when income rises, which most lenders allow.
Flat rate and reducing balance are not comparable
This is the single most common way borrowers are misled, and it is not usually illegal — the numbers are stated, just in different currencies.
Under a reducing-balance rate, interest is charged on what you still owe. Under a flat rate, interest is charged on the original principal for the whole term, regardless of how much you have repaid.
Borrow ₹5,00,000 for three years:
- Flat 8%: interest is ₹5,00,000 × 8% × 3 = ₹1,20,000. The EMI is ₹17,222.
- Reducing-balance 8%: the EMI is ₹15,668, and total interest is ₹64,055.
Same headline number, nearly double the cost. As a rule of thumb, a flat rate is roughly equivalent to a reducing rate of 1.8 to 2 times its stated value. That 8% flat is somewhere near 14.5% reducing.
Home loans and most personal loans from banks are reducing-balance. Flat rates turn up in vehicle loans from dealers, consumer-durable finance and some non-bank lenders. If you are comparing two offers, convert both to reducing-balance or compare the total repaid — never compare the two rates directly.
Fixed, floating, and what actually moves
On a fixed-rate loan the rate is agreed for the term, so the EMI genuinely does not change.
On a floating-rate loan the rate is tied to an external benchmark — for most Indian retail loans since 2019 that is the RBI repo rate, plus the lender's spread. When the benchmark moves, something has to give. Lenders overwhelmingly choose to change the tenure and keep the instalment, because a borrower notices a higher EMI immediately and barely notices four more years of payments.
The consequence is worth stating plainly: after a series of rate rises, a twenty-year loan can quietly become a twenty-six-year loan while the monthly figure on your statement never changes. You are entitled to ask for the instalment to be raised instead, and it is usually the cheaper choice.
Prepayment: which lever to pull
When you prepay a lump sum, you get a choice, and the default is rarely the better one.
- Keep the EMI, shorten the tenure. The instalment stays where it is, and the loan ends sooner. Interest saved is large, because you stop paying it years early.
- Reduce the EMI, keep the tenure. The monthly figure falls, the end date does not move. This helps cash flow and saves comparatively little.
On our ₹10,00,000 at 9.5% over ten years, prepaying ₹1,00,000 at the end of year two:
- Keeping the EMI ends the loan 15 months early and saves roughly ₹1,01,000 in interest.
- Reducing the EMI drops it by about ₹1,490 a month and saves roughly ₹43,000.
Most lenders apply the second unless you ask for the first in writing. Ask.
Two rules govern prepayment in India and are worth knowing before you sign:
- On floating-rate loans to individuals, banks may not charge a foreclosure or prepayment penalty. This is an RBI requirement, not a courtesy.
- On fixed-rate loans, penalties are permitted, and typically run 2–4% of the amount prepaid. Check the sanction letter, not the brochure.
The rate is not the cost
Two loans at the same advertised rate can differ by a large amount. Before you compare EMIs, put everything into the same number:
- Processing fee — commonly 0.5–2% of the loan, sometimes deducted from the disbursal so you receive less than you borrowed while paying interest on the full amount.
- Insurance sold alongside — often financed into the loan itself, so you pay interest on the premium for the whole term.
- Documentation, legal and valuation charges on secured loans.
- Prepayment penalties, which matter enormously if you expect a bonus or a sale.
- Conversion fees to move to a lower rate later, which floating-rate lenders charge when their own new customers are offered better terms than you.
A loan at 9.4% with a 2% processing fee is more expensive than one at 9.5% with none, on any tenure under about eight years.
Common questions, briefly
Does missing one EMI change the schedule? Yes, and more than the amount suggests. The unpaid interest is added to the balance, so you then pay interest on interest, and a late-payment penalty is charged on top. It is also reported to credit bureaus, which is usually the more expensive consequence.
Is a bigger down payment always better? It lowers both the EMI and the total interest, so financially yes — up to the point where it leaves you with no emergency buffer. An emergency funded by a personal loan at 16% wipes out the saving from a larger down payment at 9%.
Can I use this calculator for a car or personal loan? Yes. The formula is identical for any reducing-balance loan; only P, r and n differ. Check that the rate you enter is reducing-balance and not flat, because vehicle and consumer finance is where flat rates are most common.
Why does my lender's number differ by a few rupees? Rounding, and the treatment of the first period. Some lenders charge broken-period interest from the disbursal date to the first instalment date, which shifts the schedule slightly. A difference of a few rupees is normal; a difference of hundreds means you are comparing different terms.
What this calculator assumes
Being explicit about assumptions is the difference between a tool and a guess:
- Interest is compounded monthly on the reducing balance, which is how Indian retail lending works.
- The rate is constant for the whole tenure. A floating-rate loan will not follow this exactly.
- Every instalment is paid in full and on time.
- Fees, insurance and taxes are excluded — enter the amount actually disbursed as the principal.
- The first instalment is one full month after disbursal, with no broken-period interest.