The EMI page, then the prepayment the EMI page refused
The EMI calculator already does the closed formula and the first twelve months. Its FAQ used to say prepayment was not modeled. This page is that model: keep the same EMI, throw extra rupees (or dollars) at principal, watch tenure and total interest fall. Month 1’s instalment is the same function — P × r × (1+r)^n / ((1+r)^n − 1) — so a screenshot of both pages with the same P, r, and n should agree before any extra is typed.
This is a worldwide calculator. Currency is required. I will not default-lock the display to INR. Pick INR, USD, EUR, or GBP; grouping and amount-in-words on the printed totals follow that code. Indian search volume is not a reason to print ₹ on a dollar loan.
Worked example
Principal 50,00,000, 8.5%, 20 years, currency INR. Month-1 EMI should match the EMI calculator (near ₹43,000). Add ₹5,000 extra monthly and the tenure shortens; the “interest saved” cell is original total interest minus the prepaid path. A lump sum in month 12 is applied on top of that month’s EMI. If your bank cuts EMI instead of tenure, this page is the wrong product — it keeps the instalment and ends the loan sooner.
CSV
Optional full schedule, generated in the tab. Banks still round each month, add fees, and reprice floating rates. A prepayment clause can charge you for the privilege of paying them back. Read the sanction letter after you play with the strip.
Questions
Does month-1 match the EMI calculator?
Yes, for the same principal, annual rate, and tenure in months. Both use EMI = P × r × (1+r)^n / ((1+r)^n − 1) with r = annual/12/100. Verify by typing the same three numbers on both pages.
What does extra monthly do?
Keeps the original EMI and adds the extra to principal each month, which cuts tenure and interest. Some banks instead cut the EMI and keep tenure; this page models the tenure-cut path.
Lump sum?
Applied in the month number you type, on top of that month’s EMI (and extra monthly if any).
Currency?
Required. INR, USD, EUR, or GBP — same set as the EMI page. Nothing is rupee-locked. Amounts and any words follow the currency you pick.
CSV?
Downloads the full schedule in this tab. No upload.
Fees and floating rates?
Not modeled. A part-prepayment charge can eat the “interest saved” headline.