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. That compounds - each overpayment saves interest for the whole remaining term, which is why even modest regular overpayments can knock years off and save thousands.
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 fixed-rate mortgages allow penalty-free overpayments of up to 10% of the balance a year; above that an early repayment charge (ERC) may apply. This calculator shows the interest maths only - check your lender's overpayment allowance and any ERC before overpaying.