Should you overpay on your mortgage or invest the spare cash? Our mortgage comparison spreadsheet lets you compare 4 options side by side. The Excel spreadsheet provides comparisons of different deposit amounts, monthly payments, total interest, investment value, and final net position. This product is suitable for first-time buyers weighing deposits against interest rates, homeowners deciding between overpaying or investing spare cash and anyone remortgaging. The spreadsheet consists of 9 sheets:

Instructions – how to use the spreadsheet and the underlying assumptions.
How it works – how the calculations work.
Overpay vs Invest – The main question of whether to overpay the mortgage or pay the basic payment and invest the difference.
Month-by-month amortisation – see the breakdown of the monthly figures for the overpay vs invest option.
Different deposits – see how different deposit amounts impact the figures – four comparisons.
Deposit amortisation – a monthly breakdown of amortisation figures for different deposit amounts.
Custom comparison – this lets you enter a full mix of house price, deposit, mortgage term, interest rate, expected investment return and extra payments for comparison.
Custom Strategies – four independent options, each running figures for three different payment strategies.
Opportunity cost – a quick one-year illustration of what overpaying vs investing costs in forgone amounts.

Details:

The product is a Microsoft Excel spreadsheet, instant download. The spreadsheet calculations accommodate mortgages up to a 30-year term. The spreadsheet assumes any investment contributions are made within a tax-free stocks and shares ISA. The spreadsheet does not include any potential tax liability on investment returns. The product includes a Word document that explains the calculator’s underlying assumptions.

Mortgage amortisation

Overpay or invest – mortgage comparison spreadsheet