Mortgage Overpayment Calculator 2026
See how much interest you save and how many years you cut off your mortgage by overpaying - a regular monthly extra, a lump sum, or both.
See how much interest you save and how many years you cut off your mortgage by overpaying - a regular monthly extra, a one-off lump sum, or both. Enter your outstanding balance, rate and years remaining. See also: mortgage repayment calculator.
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Frequently asked questions
How does overpaying a mortgage save money?
Overpayments come straight off the outstanding balance, so you are charged interest on a smaller amount every month afterwards. If your lender keeps the monthly payment the same, more of each payment goes to capital, so the term shortens and the interest saving builds up over the remaining term. Some lenders reduce the monthly payment instead, which saves less interest.
Is a lump sum or a regular overpayment better?
Both help; earlier is better because the saving compounds for longer. A lump sum today removes interest on that amount for the entire remaining term. A regular monthly overpayment builds the same effect steadily. This calculator lets you model either or both together.
Are there limits on overpaying?
Many mortgages, especially fixed-rate deals, limit how much you can overpay each year without an early repayment charge (ERC). The allowance is set by your lender and is in your mortgage offer. This calculator shows the interest maths only - check the allowance and any ERC before overpaying.