1. What is a part-prepayment?
A part-prepayment is any payment you make toward your loan that's over and above your scheduled EMI. It can be a single lump sum, a recurring monthly extra, or a combination. The entire extra amount goes directly to reducing your outstanding principal — never toward interest.
Because interest is calculated on the outstanding balance, any part-prepayment immediately reduces the base on which future interest is charged. The result: you pay less total interest and (usually) finish the loan sooner.
2. Why comparing scenarios matters
Not all prepayments are created equal. Two strategies with the same total cash outflow can produce very different savings. For example:
- A ₹2 lakh lump sum in year 5 might save ₹4.5 lakh in interest.
- ₹5,000/month for 40 months (also ₹2 lakh total) starting in year 1 might save ₹5.5 lakh.
- A ₹2 lakh lump sum in year 10 might only save ₹2.8 lakh.
Same money, very different outcomes. That's why comparing scenarios is valuable — the best answer isn't always the most obvious one.
💡 Rule of thumb: the earlier your money lands on the principal, and the more frequently you pay, the more interest you save — for the same total cash outlay.
3. How to set up meaningful scenarios
The three scenario slots in this calculator are designed to let you compare the trade-offs that actually matter. Here are some useful ways to structure them:
- Same amount, different timing: ₹2 lakh in year 1 vs. year 5 vs. year 10. Shows how much timing matters.
- Lump sum vs. monthly: ₹3 lakh lump sum vs. ₹10,000/month for 30 months vs. both.
- Do nothing vs. modest vs. aggressive: Baseline, ₹50,000 lump sum, ₹2 lakh lump sum. Shows the diminishing returns of larger prepayments.
- Different milestones: What if you prepay after a bonus at year 1 vs. at year 3 vs. at year 5?
4. Why earlier is almost always better
Reducing-balance interest is front-loaded. On a typical loan, more than half the total interest is charged in the first third of the tenure. Once that interest has been paid, prepaying only affects the smaller remaining balance, so it saves less.
This is why a ₹1 lakh prepayment in month 6 typically saves 3–4x more interest than the same prepayment in month 120. The math is unforgiving: the earlier you act, the bigger the reward.
5. Cost of prepayment
Prepayment isn't always free. Depending on your loan type:
- Floating-rate home loans: No prepayment penalty for individual borrowers (RBI rule).
- Fixed-rate loans: Often a penalty of 1–2% of the prepaid amount.
- Personal loans: Frequently 2–4% prepayment penalty.
- Car loans: Varies — many lenders now allow free prepayment.
If your lender charges a penalty, the true savings are reduced by that cost. The best scenario is the one with the highest net benefit, not just the highest gross savings.
6. Reduce tenure vs. reduce EMI
When you prepay, your lender typically gives you two options:
- Reduce tenure: Your EMI stays the same, but the loan closes earlier. Saves the most interest.
- Reduce EMI: Your tenure stays the same, but your monthly payment drops. Improves cashflow but saves less interest.
Unless cashflow is a genuine problem, reduce tenure is usually the better choice. The difference in total interest saved can be 40–60% higher.
7. When prepayment doesn't make sense
- You don't have an emergency fund. Build 6–12 months of expenses first.
- You have high-interest credit card debt. Pay that off — it costs 3–4x more than any loan.
- Your loan rate is very low. If you have a 4% home loan and can earn 10% in equity markets, investing may beat prepaying.
- You'd lose significant tax deductions. Home loan interest is deductible up to ₹2 lakh/year — a real subsidy that prepaying erases.
8. A worked comparison
Take a ₹20 lakh loan at 9% for 15 years. Monthly EMI: ₹20,285. Total interest if untouched: ₹16.51 lakh.
- Scenario A — ₹1L in month 12: Saves ~₹1.9L interest, closes 8 months early.
- Scenario B — ₹2L in month 24 + ₹3,000/month: Saves ~₹4.4L interest, closes 2 years early.
- Scenario C — ₹5L in month 60: Saves ~₹3.6L interest, closes 1.6 years early.
Notice how Scenario B — with a smaller lump sum than C — saves the most. That's the monthly extra working in its favour: it keeps reducing the balance from month 1, whereas C waits until month 60 before making a move.
✓ Consistent monthly extras often beat a larger one-off lump sum later in the loan. If you have the cashflow, recurring prepayments are powerful.
9. How to use this calculator
- Enter your loan amount, rate, and tenure.
- For each scenario, enter a lump sum amount and the month you'd pay it.
- Optionally add a monthly extra that continues until the loan closes.
- Toggle scenarios on/off to compare different combinations.
- Review the comparison table — the winning scenario is highlighted.
- Scroll down to see how each scenario plays out year by year.
10. Final thoughts
Part-prepayment is one of the highest-return, lowest-risk financial moves available to most borrowers. Every rupee you prepay earns a guaranteed, tax-free return equal to your loan's interest rate. For most people, that's a return they can't reliably beat in markets — especially on a risk-adjusted basis.
The catch is liquidity. Prepayment locks your money into debt reduction — you can't easily get it back. That's why the right answer depends on your emergency fund, job stability, investment opportunities, and psychological comfort with debt. Run the scenarios in this calculator, then choose what fits your life.