Methodology
How every number on this site is produced — and how we check it. Last updated 24 June 2026.
emi.me exists to be the calculator you can actually trust, because you can see exactly how it works. This page documents the formulas, the assumptions behind each tool, and how we verify the maths. If you ever find a discrepancy, tell us — corrections matter more to us than being right the first time.
The reducing-balance EMI formula
Every EMI on this site uses the standard reducing-balance method:
EMI = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)where P is the principal, r is the monthly interest rate (annual rate ÷ 12 ÷ 100) and n is the tenure in months. "Reducing balance" means interest in any month is charged only on the balance still outstanding. When the rate is exactly 0% (a genuine no-cost EMI), the formula reduces to P ÷ n so there is no division by zero.
How the amortization schedule is built
We step through the loan month by month. Each month's interest is the opening balance times the monthly rate; the rest of the EMI reduces the principal; the balance carries forward. The final instalment is trimmed so the balance lands exactly on zero rather than overshooting. The schedule you see — whether yearly summary or every month — is this exact computation, not an approximation.
How prepayments are modelled
A part-payment is applied straight to the outstanding principal in the month you specify (one-time or recurring). You choose how the benefit is taken:
- Reduce tenure (keep the EMI): the loan simply closes earlier. This saves the most interest and is the default.
- Reduce EMI (keep the tenure): the instalment is recomputed over the remaining original term, lowering each future payment.
"Interest saved" and "months saved" are the difference between the schedule with your prepayment and the untouched baseline.
The prepay-vs-invest model
The prepay-vs-invest tool compares two uses of the same monthly surplus. In the prepay path, the surplus clears the loan early, after which the freed-up EMI plus surplus is invested to the horizon. In the invest path, you pay the normal EMI and invest the surplus throughout. Investment growth uses a level monthly contribution (an ordinary annuity) at a constant return. The break-even return — where both leave you equally wealthy — is found numerically and sits near your loan rate, because prepaying is mathematically a guaranteed return equal to that rate. The model is deliberately pre-tax and ignores market volatility; we say so on the tool itself.
Verification: a unit-tested engine
The calculation engine is covered by an automated test suite. Expected values were computed independently (in a separate environment, to full double precision) before the engine was written, so the tests check the code against an outside source of truth rather than against itself. A few of the hand-verified cases:
| Loan | Rate | Tenure | EMI |
|---|---|---|---|
| ₹1,00,000 | 10% | 12 months | ₹8,791.59 |
| ₹5,00,000 | 12% | 24 months | ₹23,536.74 |
| ₹8,00,000 | 9.5% | 60 months | ₹16,801.49 |
| ₹10,00,000 | 8.5% | 240 months | ₹8,678.23 |
| ₹1,20,000 | 0% | 12 months | ₹10,000.00 |
The suite also checks that schedules close to zero, that totals reconcile (EMI × n = principal + interest), and that prepayment savings and the prepay-vs-invest break-even behave correctly.
Sources, standards and honesty
The reducing-balance method is the standard for retail lending in India and globally. Where we describe regulatory points — for example that the Reserve Bank of India bars prepayment and foreclosure penalties on floating-rate home loans taken by individuals, or that "zero-interest" schemes are not truly free — we state them as general information and tell you to confirm against your own sanction terms. Default interest rates in the calculators are realistic mid-range values used only as a sensible starting point; they are not quotes, offers, or predictions.
We hold ourselves to a few hard rules:
- No fabricated statistics, and no fake review counts or star ratings anywhere on the site.
- No "best lender" rankings driven by affiliate payouts.
- Every worked example uses a figure produced by the tested engine, not a number we made up.
Editorial and updates
Content is written and maintained by the emi.me Editorial team and reviewed against this methodology before publishing. Each guide carries its own published and last-updated dates. emi.me is independent: we are not a lender, broker or financial adviser, and nothing here is personal financial advice. Figures are estimates to confirm with your bank before you decide.