Mortgage Overpayment Calculator

Introduction

The Mortgage Overpayment Calculator estimates how extra payments could reduce interest and shorten the life of a repayment mortgage. It is for borrowers who want to compare a regular overpayment, a lump sum, or both against the current repayment path.

About this mortgage overpayment tool

Overpaying can be powerful because it reduces the balance that future interest is charged on. The benefit depends on interest rate, remaining term, overpayment size, and lender rules. Seeing time saved and interest saved side by side helps you compare overpaying with saving, investing, or keeping cash available.

How this tool works

The tool estimates the current monthly repayment from balance, rate, and term, then simulates the mortgage month by month with and without your extra payments. The difference between the two paths becomes the estimated interest saved and earlier payoff date.

1. Enter your current mortgage balance, interest rate, and remaining term.
2. Add a monthly overpayment and optional one-off overpayment.
3. Compare the estimated payoff time and interest with and without overpayments.

When to use this tool

Use it before setting a standing overpayment, using a bonus, or reviewing a remortgage plan. Check overpayment limits, early repayment charges, emergency savings, and whether higher-interest debt should be cleared first before acting on the estimate.

Good to know

• The result assumes a constant rate, repayment mortgage, and no changes to fees or payment rules.
• Check your lender's overpayment allowance and early repayment charges before making extra payments.