Mortgage overpayment calculator

See how much interest you could save, and how much sooner you could be mortgage-free, by overpaying a repayment mortgage. Add a regular monthly overpayment, a one-off lump sum, or both. All calculations run in your browser — nothing is sent anywhere.

Outstanding balance (£)

Interest rate (%)

Remaining term (years)

Start date

Monthly overpayment (£)

Monthly overpayments start in month Month 1 is the first payment. Use 13 to start after a year, for example.

Overpayments should

One-off lump sum (£)

Lump sum paid in month

Penalty-free overpayment allowance (% per year) Many lenders allow around 10% of the balance each year without an early repayment charge. Check your own mortgage terms. Years that go over this are flagged.

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interest saved

Comparison

Balance over time

Year by year

Disclaimer: This calculator is for illustrative purposes only. It does not constitute a mortgage offer or financial advice. It assumes a fixed interest rate for the whole term and monthly interest compounding, and ignores fees and early repayment charges. Your lender's actual figures will differ.