Mortgages & property
Mortgage overpayment calculator
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See how much interest you could save, and how many years you could cut off your mortgage, by overpaying each month or making a one-off lump sum payment.
- Interest saved
- £29,633
- Time saved
- 5 yr 3 mo
- New payoff time
- 19 yr 9 mo
| Normal monthly payment | £1,000.50 |
|---|---|
| With overpayment | £1,150.50 |
| Interest without overpaying | £120,150 |
| Interest with overpaying | £90,516 |
| Original term left | 25 yr 0 mo |
| Total interest saved | £29,633 |
Estimates assume your interest rate stays the same for the whole term, which it usually won't once your current deal ends. Most lenders let you overpay up to 10% of the balance each year without an early repayment charge (ERC) — check your mortgage terms before making large overpayments. Always keep an emergency fund rather than overpaying every spare pound.
How it works
- We first work out your normal monthly payment from your balance, interest rate and remaining term using the standard repayment formula.
- We then run two schedules month by month: one at your normal payment, and one with your overpayment (and any lump sum) added. Each month we add interest, subtract the payment, and continue until the balance reaches zero.
- The difference between the two schedules is your interest saved and the time knocked off your mortgage.
Common questions
- Is it better to overpay or to save the money?
- If your mortgage rate is higher than the interest (after tax) you'd earn on savings, overpaying usually wins financially. But always keep an accessible emergency fund first — money overpaid into a mortgage is hard to get back.
- Will overpaying reduce my monthly payment or my term?
- Most lenders keep your payment the same and shorten the term by default, which saves the most interest. Some let you choose to lower the monthly payment instead — ask your lender which applies.
- What is an early repayment charge?
- An ERC is a fee — often 1% to 5% of the amount overpaid — that some lenders charge if you overpay above the annual allowance during a fixed deal. Check your mortgage offer before making large overpayments.