Mortgage Overpayment Comparison
Monthly overpayment vs lump sum vs none, months and interest saved, verified
The same mortgage run three ways side by side, no overpayment, a fixed monthly overpayment, a one-off lump sum, with the months and interest each one saves.
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Enter the balance, rate and remaining term, a fixed monthly overpayment for scenario B and a lump sum with its month for scenario C. The workbook runs all three for up to 480 months: interest on the opening balance, the contractual payment (never more than balance plus interest), the extra, the closing balance. The Comparison sheet puts them side by side: months and years to clear, total interest, total paid, total extra, the saving of B and C against A, and interest saved per unit of extra paid, so a monthly overpayment and a lump sum compare on the same footing.
- All three schedules and every comparison line recalculated with a formula engine and matched to an independent Python replica before listing.
- Live formulas, no macros, no locked cells; opens in Excel and Google Sheets.
- Overpayment allowances, early repayment charges, rate changes at the end of a fix, and offset accounts are outside the workbook and the Guide says so. Arithmetic on your own numbers, not financial advice.
What is inside
1 Excel workbook (.xlsx), sheets: Inputs, Comparison, A no overpayment, B monthly overpayment, C lump sum (480 months each), Guide.
Use it if
You are deciding whether and how to overpay a mortgage and want the arithmetic shown month by month.
Not for
You need a remortgage comparison across products with fees and fixed periods; this compares overpayment strategies on one loan.
Sheet previews
How buying works
- Choose a licenceSingle user for one person, team for up to 10, consultancy to use with clients. The buttons above go to the Gumroad page.
- Pay on GumroadCard or PayPal; Gumroad is the merchant of record and handles VAT and the receipt.
- Download the fileThe .xlsx arrives on the receipt page and by email. It opens in Excel and Google Sheets; nothing to install.
- Use itYellow cells are inputs, blue cells are formulas, every figure names its source. Questions: reply to the receipt; every reply is read and answered, usually the same day.
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