Home loan EMI: how it is calculated and how tenure changes it

An EMI, or equated monthly instalment, is the fixed amount you pay each month to repay a home loan with interest. It is set by three things: how much you borrow, the interest rate and the number of months. A ₹50 lakh loan at an illustrative 8.5% a year over 20 years works out to an EMI of about ₹43,391. This guide shows the formula, works through that example, and explains why tenure, rate changes and prepayments matter so much to the total you pay.

The formula

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

• P is the amount borrowed.
• r is the monthly interest rate: the annual rate divided by 12, then by 100. At 8.5% a year, r = 8.5 ÷ 1,200 = 0.0070833.
• n is the number of monthly instalments: 240 for 20 years.

Interest is worked out each month on the balance still outstanding, which is why a home loan is called a reducing-balance loan; banks charge interest at monthly rests. The RBI's own model Key Facts Statement uses the same method: its sample loan of ₹20,000 at 15% over 24 months has an instalment of ₹969.73.

A worked example (illustrative)

Assumptions, for illustration only: a loan of ₹50 lakh at 8.5% a year for 20 years, with the rate unchanged throughout. The rate is chosen to make the arithmetic concrete; it is not a quote or a forecast.

• (1 + r)^240 = 5.4412
• EMI = 50,00,000 × 0.0070833 × 5.4412 ÷ 4.4412 = ₹43,391 (rounded)
• Total paid over 20 years: about ₹1.04 crore
• Total interest: about ₹54.1 lakh, more than the amount borrowed

Your lender's figures may differ slightly because of rounding; the repayment schedule in your Key Facts Statement is the one that counts for your loan.

Why the early EMIs are mostly interest

Each month, interest on the outstanding balance is paid first, and only the rest of the EMI repays principal. In the example, the first month's interest is ₹50,00,000 × 0.0070833 = ₹35,417, so only ₹7,974 of the first EMI reduces the loan.

Over the first year, about ₹4.21 lakh of the ₹5.21 lakh you pay is interest, roughly four rupees in every five. After five years you will have paid about ₹26 lakh but cut the balance by only about ₹5.9 lakh. The principal part of the EMI overtakes the interest part only at the 143rd EMI, in the twelfth year, and the balance falls below half the original loan in the fourteenth year.

The early years of a home loan mostly pay interest, which is why money prepaid early saves the most.

How tenure changes the EMI and the interest

The same ₹50 lakh at 8.5%, illustrative:

Stretching from 20 to 30 years cuts the EMI by about ₹4,945, around 11%, but adds about ₹34.3 lakh of interest. Going from 20 to 15 years costs ₹5,846 more a month and saves about ₹15.5 lakh. A longer tenure can make a loan possible, but at the same rate it always costs more interest.

When the rate changes: EMI or tenure

With a floating rate, each reset changes either your EMI or the number of EMIs, and when rates rise the RBI's rules let you choose a higher EMI, a longer tenure or a mix. Fixed vs floating home loan rates explains how resets work. Here is the example loan after five years, with 60 EMIs paid, about ₹44.06 lakh outstanding and 180 EMIs left at 8.5%:

Keeping the EMI feels painless but costs more. At 9.0%, stretching the tenure means about ₹39.2 lakh of interest over the rest of the loan; raising the EMI instead means about ₹36.4 lakh, against ₹34.0 lakh had the rate stayed at 8.5%. The RBI also requires that a longer tenure never leaves the EMI too small to cover the interest, so the balance cannot grow.

What a part-prepayment does

Prepaying reduces the balance on which interest is charged. Continuing the example, suppose you prepay ₹5 lakh after 60 EMIs:

Shortening the tenure saves more; lowering the EMI eases your monthly budget. Banks and housing finance companies cannot charge you for prepaying a floating-rate home loan, so even small, regular prepayments are worth considering. Balance transfer, prepayment and foreclosure covers the rules and the closure paperwork, and our guide to how home loans work covers the rest of the loan's life.

Affordability habits

There is no single right EMI. Many lenders compare your total EMIs with your income, but the most a lender will approve is not the same as what is comfortable for you. A few habits help:

• Work out the EMI at a rate one to two percentage points above today's, and check you could still pay it.
• Keep a reserve of several months' EMIs and household costs before you commit.
• Count the whole cost of buying: down payment, stamp duty, registration, moving and furnishing.
• Choose the shortest tenure you can comfortably manage, and use prepayments to shorten it further.
• If you are buying to let, plan to pay the EMI without the rent, because a let home can sit empty between tenants. Rental yield and cash flow and our page for owners can help you plan.
• Read your quarterly statement: it shows the principal and interest paid so far, the EMI, the number of EMIs left and the annualised rate.

Before you sign, ask for the full repayment schedule in the Key Facts Statement and check it against your own calculation; if the two differ by more than a little rounding, ask the lender why.

Frequently asked questions

Does a longer tenure ever reduce the total interest?

No. At the same rate, a longer tenure always means more interest, because the balance is repaid more slowly. It lowers the EMI, which can make a loan affordable, and you can shorten it later with prepayments.

Should a prepayment reduce my EMI or my tenure?

Reducing the tenure saves more interest; reducing the EMI gives you more room each month. In the example above, the same ₹5 lakh saves about ₹10.7 lakh one way and about ₹3.9 lakh the other.