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Mortgage Overpayment Calculator
Your mortgage
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%
yrs
£
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How it works
Each extra £ goes 100% to principal, reducing future interest charges. The earlier you overpay, the more interest you avoid — overpayments in year 1 save much more than the same amount in year 20.
Worked example
£180k at 4.5% over 22 years: £1,074/mo, £103,544 total interest. Adding £150/mo extra: clears in 17.6 years, saves ~£28,000 interest.
Who should use this
- •Anyone with spare cashflow each month
- •Borrowers near the end of a fix who want to reduce balance before remortgaging
- •Pre-retirees clearing the mortgage
Common mistakes
- ×Overpaying past the lender's allowance and triggering ERCs (typically 1–5%)
- ×Overpaying when high-interest debt (credit cards) still exists
- ×Forgetting an emergency fund — overpayments are hard to get back
Frequently asked questions
Should I overpay or invest?▾
Mathematically: invest if expected returns > mortgage rate after tax. Emotionally: many prefer the certainty of a smaller mortgage.
Reduce term or reduce monthly?▾
Reducing the term saves more interest. Reducing monthly gives flexibility but lets the loan run full term unless you keep overpaying.