Mortgage affordability:
from monthly budget to loan size

The reverse EMI formula

Most buyers fix on a property price and then check whether the loan fits. The safer route is the reverse: decide the monthly instalment your household can carry without strain, and ask what loan that instalment can repay at today's rate and your chosen tenure.

The answer is a ceiling, not a target. It describes the largest principal for which the principal-and-interest payment equals your budget; taxes, insurance, registration, maintenance and fees come on top and are not in this figure.

The bracket is a discount factor. It converts a stream of equal payments over n months into what that stream is worth today at the loan rate, which is exactly the amount a lender will advance against it.

Worked example: ₹35,000 a month

Put another way, each ₹1 lakh borrowed costs about ₹836 a month at these terms, and 35,000 ÷ 836 gives the same ₹41.8 lakh.

How rate and tenure move the ceiling

Holding the ₹35,000 budget and an 8% rate, a longer tenure supports a larger loan, but with sharply diminishing returns.

Going from 20 to 30 years raises the borrowing power by only about ₹5.9 lakh while adding ₹42 lakh of total payments. Rate matters as much: at 7% the same budget supports about ₹45.14 lakh, and at 9% about ₹38.90 lakh.

From loan to property price

The loan is only part of what you can buy. If the lender finances at most 80% of the value, a ₹41.84 lakh loan implies a property of about 41.84 ÷ 0.80 = ₹52.3 lakh, with the remaining 20% from your own funds. The maximum loan-to-value ratio and permitted loan share vary by lender and loan size, so confirm the current rule.

• Down payment: your savings set the other side of the purchase price.
• Stamp duty and registration: often several percent of the price and usually not financed.
• Moving, furnishing and a cash buffer for the first months.

Fixed versus floating rates, and prepayment

The formula treats the rate as constant for the whole tenure. Many home loans in India are floating, linked to an external benchmark or the lender's own rate, which means the instalment or the tenure moves when the rate does. When rates rise, lenders commonly keep the EMI the same and lengthen the tenure, which hides the damage until you read the statement.

Prepayments work in your favour. Paying an extra ₹1 lakh early in the loan removes the interest that would have accrued on it for the rest of the term, which at 8% over many years can be substantial. Many lenders do not charge prepayment penalties on floating-rate loans to individuals, but the policy and any conditions depend on the lender and loan type, so confirm before you plan around it.

Costs that sit outside the EMI

An affordability figure that stops at the instalment gives a falsely comfortable picture of living in the home. A number of recurring and one-time costs do not appear in the loan formula at all.

• One-time: stamp duty, registration, brokerage, legal and technical checks, and the lender's processing fee.
• Recurring: property tax, society maintenance, utilities and repairs, which can run into several thousand rupees a month.
• Insurance: home insurance and, where taken, loan life cover.
• Interiors and moving: often underestimated and usually paid from savings.

A sensible habit is to add the recurring ones to the EMI and test whether the total still fits the monthly budget. If the instalment is ₹35,000 and recurring costs are ₹5,000, you are really spending ₹40,000 a month on housing, and the ceiling on the loan should come down accordingly.

Using the result with a lender

Walk into a bank branch with a number and you start from a stronger position. Knowing that ₹35,000 a month supports about ₹41.8 lakh at 8% over 20 years lets you ask how a quoted rate, tenure and fee structure compare. It also lets you check the lender's own offer: if they quote an EMI of ₹36,500 for the same loan, you can see how much of that difference comes from the rate or tenure.

Ask for the loan's full cost, not just the rate: processing fees, insurance bundled in, the rate-reset rule and any charge on part-payment or foreclosure. Compare offers by the total amount paid and by the interest rate together. Two offers with the same headline rate can differ by lakhs once fees and add-ons are counted.

Stress-test the figure before you rely on it

Floating rates can rise. If the rate on the same ₹41.84 lakh loan climbed from 8% to 10%, the instalment would go to about ₹40,380, an increase of ₹5,380 a month, or about 15%. Ask yourself whether the household could absorb that without cutting the savings that protect against a job gap or a medical bill.

Lenders usually apply their own rules, such as limiting existing and new EMIs to a share of take-home income. As an illustration only, if a lender allowed obligations up to half of ₹90,000 in monthly income and you already paid ₹10,000 on other loans, the room for a new EMI would be ₹35,000, the budget used above. Your lender's actual limit and your own comfort level may well be lower.