See exactly what overpaying your mortgage achieves: the interest you will save, the years you will knock off a repayment mortgage, and how much of an interest-only balance you can clear. Works for both repayment and interest-only mortgages.
Your mortgage
£
%
yrs
Overpayments
£
£
Most lenders allow penalty-free overpayments of up to 10% of the balance a year. Check for an early repayment charge if you’re in a fixed deal.
Interest saved
£36,278
6 years 1 month off your mortgage
Normal monthly payment£1,112
New monthly payment£1,312
Original time remaining25 years
New time to clear18 years 11 months
Time saved6 years 1 month
Interest without overpaying£133,498
Interest after overpaying£97,220
Interest saved£36,278
Overpaying clears your mortgage 6 years 1 month sooner and saves £36,278 in interest.
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How overpayments work
Every overpayment comes straight off your outstanding balance, so you stop paying interest on that money for the rest of the term. Because mortgage interest compounds, overpaying early has an outsized effect - a modest regular overpayment can take years off a repayment mortgage and save tens of thousands in interest.
Repayment mortgage: your monthly payment stays the same, but more of it clears capital, so the mortgage ends sooner and total interest falls.
Interest-only mortgage: overpayments reduce the capital you would otherwise owe in full at the end - and cut the interest you pay along the way.
A one-off lump sum (e.g. a bonus or inheritance) and regular monthly overpayments can be combined here.
Worked example - repayment
200,000 balance at 4.5% with 25 years left gives a normal payment of about 1,112/month.
Overpay 200/month and you clear it roughly 6 years early...
...saving around 36,000 in interest over the life of the mortgage.
Most lenders let you overpay up to 10% of the balance each year without penalty. If you are inside a fixed deal, check for an early repayment charge (ERC) before making large overpayments, and confirm whether your lender reduces the term or the monthly payment when you overpay.
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Frequently asked questions
Should I overpay the mortgage or save/invest instead?
Compare your mortgage rate with the after-tax return you could earn elsewhere. If your mortgage costs more than a guaranteed savings rate, overpaying is effectively a risk-free return at your mortgage rate. Clearing expensive non-mortgage debt usually comes first, and keep an emergency fund before overpaying.
Does overpaying reduce my term or my monthly payment?
It depends on your lender. Reducing the term keeps payments the same and saves the most interest; reducing the payment gives you monthly breathing room but saves less. This calculator assumes you keep paying the same amount (term reduction) for a repayment mortgage.
Is there a limit on overpayments?
Most lenders allow penalty-free overpayments of up to 10% of the outstanding balance per year. Beyond that - or while in a fixed deal - an early repayment charge may apply, so always check your mortgage terms.
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Important: BrickCrunch provides general information and estimates only — this is not financial, tax, mortgage or legal advice. Calculations are simplified and your circumstances may differ. UK tax and rate figures are checked against gov.uk (21 June 2026 (2026/27 tax year)) but rates change and errors are possible. Always confirm figures with gov.uk or a qualified professional before making decisions.
