Loan Prepayment Calculator

Loan Prepayment Calculator: See Exactly What Part-Payment Saves You

A Loan Prepayment Calculator shows how much interest you save and how many months you knock off your loan when you pay an extra lump sum over and above your regular EMI. It works for home loans, car loans, personal loans and business term loans — any loan on a reducing-balance (EMI) basis. It is built for borrowers who have received a bonus, an annual increment, matured investments, or simply have surplus cash and want to know whether throwing it at the loan is worth it compared with keeping the loan running.

What "prepayment" actually does

Every EMI you pay is split into an interest part and a principal part. In the early years, most of the EMI is interest because interest is charged on the full outstanding balance. A part-prepayment goes straight against the principal. Because interest is calculated on a smaller balance from that day on, the same EMI now clears the loan faster. You typically get two choices from the lender: keep the EMI the same and reduce the tenure (this saves the most interest), or keep the tenure and reduce the EMI (this eases monthly cash flow). Reducing tenure is almost always the bigger money-saver.

The formula in words

First the EMI itself: EMI = P x r x (1+r)^n / ((1+r)^n minus 1), where P is the principal, r is the monthly interest rate (annual rate divided by 12, expressed as a decimal), and n is the number of months. When you prepay, the calculator subtracts the lump sum from the current outstanding balance to get a new balance B. If you keep the EMI unchanged, the new number of remaining months is found by solving the same equation for n, which reduces to n(new) = minus ln(1 minus (B x r) / EMI) / ln(1 + r). The true interest saved = old total interest minus new total interest — in cash terms, the fall in your EMI outgo minus the lump sum you paid in, that is (old months x EMI) minus (prepayment + new months x EMI). And tenure reduction = old months minus new months.

A fully worked example (in Rupees)

Take a home loan of Rs. 30,00,000 at 9% per year for 20 years.

• Monthly rate r = 9% / 12 = 0.0075. Months n = 240.
• EMI = 30,00,000 x 0.0075 x (1.0075)^240 / ((1.0075)^240 minus 1). Here (1.0075)^240 is about 6.009, so EMI = about Rs. 26,992.
• Without any prepayment, total repayment = 26,992 x 240 = Rs. 64,78,080, of which interest alone is about Rs. 34,78,080.

Now suppose you make a one-time part-prepayment of Rs. 3,00,000 right at the start and keep the EMI the same. The outstanding drops to Rs. 27,00,000.

• New months = minus ln(1 minus (27,00,000 x 0.0075) / 26,992) / ln(1.0075) = about 186 months (15.5 years) instead of 240.
• Total outflow now = Rs. 3,00,000 prepaid + 26,992 x 186 = 3,00,000 + 50,20,512 = Rs. 53,20,512.
• Interest saved = 64,78,080 minus 53,20,512 = about Rs. 11,57,568, and the loan ends 54 months (about 4.5 years) sooner.

A Rs. 3 lakh prepayment returning roughly Rs. 11.5 lakh in saved interest is the whole point: prepaying early, when the balance is large, is dramatically more powerful than prepaying near the end. (Note that the 54 fewer EMIs are worth 54 x 26,992 = Rs. 14,57,568 of avoided payments, but Rs. 3 lakh of that is the lump sum you put in — the net saving is Rs. 11,57,568.)

Rules and edge cases

• Floating-rate home loans: the RBI bars banks and NBFCs from charging foreclosure or part-prepayment penalties to individual borrowers on floating-rate loans not taken for business.
• Fixed-rate loans, and some business or personal loans: a prepayment/foreclosure charge (commonly 2% to 5% of the amount prepaid, plus GST) may apply. Subtract this cost before deciding.
• Lock-in and minimum amount: some lenders allow prepayment only after a few EMIs, or require a minimum multiple of one EMI.
• Get it applied to principal: confirm in writing that the lump sum reduces principal and ask for a revised amortisation schedule.

Tax treatment (India)

For a home loan under the old tax regime, principal repaid — including a prepayment — counts toward the Section 80C deduction of up to Rs. 1.5 lakh a year, and interest on a self-occupied house qualifies under Section 24(b) up to Rs. 2 lakh a year. Prepaying reduces future interest, which also reduces the Section 24(b) benefit you would have claimed, so the true "saving" is the interest saved net of the tax you were shielding. Under the new regime (the default from FY 2025-26) these deductions are generally not available for a self-occupied home, which tilts the maths further in favour of prepaying. Personal and car loans for personal use carry no such deductions.

Common mistakes and tips

• Prepay early, not late. The same rupee saves far more interest in year 2 than in year 15.
• Choose tenure reduction over EMI reduction if your goal is to save the maximum interest.
• Weigh the alternative. If a safe post-tax return beats your loan rate, investing may win; if not, prepaying is a guaranteed, risk-free "return" equal to the loan rate.
• Keep an emergency buffer. Do not drain savings to prepay and then borrow expensively later.
• Watch penalties. On fixed-rate or business loans, a foreclosure charge can erase part of the benefit. Rates and RBI rules can change, so confirm the current position with your lender.

Frequently asked questions

Is it better to reduce the EMI or reduce the tenure after prepayment?

Reducing the tenure while keeping the EMI unchanged saves the most interest, because you close the loan faster. Reducing the EMI eases monthly cash flow but you keep paying for the full remaining term, so total interest saved is smaller.

Are there prepayment or foreclosure charges in India?

The RBI does not allow banks and NBFCs to levy prepayment or foreclosure penalties on individual borrowers with floating-rate loans not taken for business. Fixed-rate loans, and many business or personal loans, may still carry a charge of roughly 2% to 5% plus GST, so check your loan agreement first.

When is the best time to prepay a loan?

As early as possible. In the initial years the outstanding balance is highest and most of your EMI goes toward interest, so a prepayment then removes far more future interest than the same amount paid near the end of the tenure.

Does prepaying my home loan affect my income tax deductions?

Under the old regime, principal prepaid counts within the Section 80C limit of Rs. 1.5 lakh, while interest is deductible under Section 24(b) up to Rs. 2 lakh for a self-occupied home. Since prepaying lowers future interest, it also lowers the Section 24(b) benefit you would have claimed; under the new default regime these deductions are generally unavailable anyway.

Should I invest my surplus or prepay the loan?

Compare your loan's interest rate with the return you can safely earn after tax. If a low-risk investment returns more than the loan rate, investing can be better; if not, prepaying gives a guaranteed, risk-free saving equal to your loan rate.

How much interest can a single part-prepayment really save?

It can be several times the amount prepaid when done early. For example, a one-time Rs. 3 lakh prepayment on a Rs. 30 lakh, 9%, 20-year home loan can save roughly Rs. 11.5 lakh in net interest and end the loan about 4.5 years sooner if you keep the EMI the same.