How is home loan EMI calculated?

EMI = P × r × (1+r)^n ÷ ((1+r)^n − 1), where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12 ÷ 100) and n is the number of monthly instalments. Every EMI is the same amount, but the split between interest and principal shifts over time.

Does prepayment reduce interest or tenure?

By default most banks keep your EMI the same and shorten the tenure, which saves the most interest. You can instead ask them to keep the tenure and lower the EMI — but that saves far less. For maximum savings, prepay early and keep the EMI the same.

Is there a penalty for prepaying a home loan?

For floating-rate home loans to individuals, the RBI does not allow foreclosure or prepayment penalties. Fixed-rate loans may carry a charge, so check your sanction letter before making a large prepayment.

When is the best time to prepay?

As early as possible. Because the early years of an EMI are mostly interest, a rupee prepaid in year one removes far more future interest than the same rupee prepaid in year ten.

How Home Loan EMI Is Calculated — And How Prepayment Cuts Your Interest (2026)

Your home loan EMI is fixed the day you sign, but how much of it is interest changes every single month. In the early years almost the entire EMI goes to interest, which is exactly why prepaying early is so powerful. This guide shows the formula, a worked ₹50 lakh example, and how even a small monthly prepayment can remove years and lakhs of interest — you can try your own numbers in the home loan EMI calculator.

The EMI formula, explained

Equated Monthly Instalment (EMI) is the fixed amount you pay every month so that the loan is fully cleared by the end of the tenure. The formula is:

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

P — the principal (the amount you actually borrow)
r — the monthly interest rate, i.e. the annual rate divided by 12 and by 100. A 8.5% loan gives r = 8.5 ÷ 12 ÷ 100 = 0.007083
n — the number of monthly instalments (20 years = 240)

The EMI itself never changes (on a fixed rate). What changes is the split: each month the bank charges interest on the outstanding balance, and whatever is left of your EMI reduces the principal. As the balance falls, the interest portion shrinks and the principal portion grows.

A worked ₹50 lakh example

Take a ₹50,00,000 loan at 8.5% for 20 years (240 months):

Figure	Value
EMI	₹43,391 / month
Total paid over 20 years	₹1,04,13,840
Of which interest	₹54,13,840

Read that again: on a ₹50 lakh loan you repay more than ₹1 crore, and the interest alone (₹54 lakh) is larger than the house you borrowed for. That is normal for a 20-year loan — and it is the number prepayment attacks.

Why the early years are almost all interest

Look at the very first EMI on that loan. Interest for month one is 0.7083% of ₹50,00,000 = ₹35,417. Your EMI is ₹43,391 — so only ₹7,974 (about 18%) actually reduces the loan. More than four-fifths of your first payment is pure interest. It takes roughly 12–13 years before the principal portion of each EMI finally overtakes the interest portion. That front-loading is the single most important thing to understand about a home loan, because it is what makes early prepayment so effective.

How prepayment slashes your interest

A prepayment is any amount you pay on top of your EMI, and it goes straight to the outstanding principal. Because next month's interest is charged on that lower balance, every rupee you prepay early removes a chain of future interest.

On the ₹50 lakh example, a modest ₹5,000 extra every month from the start roughly:

Clears the loan in about 15–16 years instead of 20
Saves in the region of ₹13–15 lakh in interest

A single lump-sum prepayment — say a ₹2 lakh bonus in year two — has a similar out-sized effect precisely because it lands while the balance (and therefore the interest) is still high. The exact saving depends on your rate and timing, so put your own EMI, rate and prepayment into the EMI calculator: it now lets you add a different prepayment in any specific month and shows the interest saved and the new payoff date live.

Reduce the tenure, not the EMI

When you prepay, the bank gives you a choice (sometimes silently defaulting one way): keep the EMI the same and finish the loan earlier, or keep the tenure the same and lower your EMI. Keeping the EMI the same and shortening the tenure saves far more interest, because your money keeps working at full strength. Only drop the EMI instead if you genuinely need the monthly cash-flow relief.

Before you sign: a quick checklist

Check	Why it matters
Floating vs fixed rate	Floating-rate loans have no prepayment penalty for individuals; fixed-rate ones can
Reset frequency	How often your rate re-prices when the repo rate moves
Processing & legal fees	Often 0.25–1% of the loan — factor it into the real cost
Prepayment process	Confirm you can prepay online and choose "reduce tenure"

A home loan is usually the largest and longest financial commitment you will make, and the interest number is far bigger than most people expect. The good news is that you have more control than you think: prepaying early, and keeping your EMI level while you do it, is the closest thing to a guaranteed, tax-free return you will find.