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Mortgage Overpayment Calculator

Updated 7 May 2023
Our calculator helps answer:
  • How much interest can you save by making a lump sum mortgage payment?
  • How quick can you repay your mortgage by increasing the monthly repayment?
  • Whether you are on track to repay your mortgage before retirement? 

Our mortgage overpayment calculator illustrates how much making an extra mortgage payment (or increasing your repayments) can save in interest costs.
mortgage overpayment calculator
Mortgage details
Current mortgage balance
This is the balance left to pay on your mortgage; you can find this on your annual mortgage statement
Remaining term
The length of time you have left to pay your mortgage, you can find this on your annual mortgage statement
Current interest rate
Your current mortgage interest rate, you can find this on your annual mortgage statement
Current monthly payment:
$0.0
Overpayment details
Regular monthly overpayment
Payments made each month that are extra to your monthly mortgage payments
- +
 
and/or
Lump sum overpayment
A one off payment made to your mortgage
- +
New monthly payment:
$0.0
Year Without overpayment With overpayment

Assumptions

​This calculator uses a number of assumptions:
  1. The model is based on a repayment mortgage - for an interest-only mortgage calculation, see our calculator. 
  2. There are no overpayment or early repayment fees - while floating mortgages don't charge this, fixed-rate deals do. Check with your lender before making any repayment.
  3. Repayments are the same every month over the entire life of the mortgage, and all years are of equal length.
  4. The interest costs are calculated daily and added monthly 
  5. The interest rate does not change over the life of the mortgage. 
Related Guides and Tools:

Mortgage Essentials:
Other Mortgage Options:
Alternative Mortgage Options:
Mortgage Management: