Mortgage Overpayment Calculator
See when your mortgage will be paid off, what overpaying could save you, and what payment you'd need to be mortgage-free sooner.
Enter your current mortgage details below — no sign-up, calculated instantly in your browser.
What would you like to calculate?
Explore other amounts
Your mortgage over time
A few points along the way, comparing your current path with the scenario you've just calculated.
How mortgage overpayments work
An overpayment is any amount you pay above your required monthly mortgage payment. Because it reduces your outstanding balance directly, less interest is charged going forward — which can shorten your mortgage term, reduce your total interest, or both, depending on how your lender applies it.
Can overpayments reduce interest?
Yes — interest is calculated on your outstanding balance, so reducing that balance sooner (whether through a lump sum or extra monthly payments) means less interest accrues over the life of the mortgage, even if your official term stays the same. If you'd rather see how your balance falls year by year at your current payment before exploring overpayments, our Mortgage Repayment Schedule Calculator shows the full breakdown.
How much can I overpay?
This varies by lender and mortgage product. Many UK mortgages allow overpayments up to 10% of the outstanding balance per year without a charge, but some allow more, less, or none at all. Always check your own mortgage agreement or ask your lender directly.
Early repayment charges
Some mortgages, particularly those on a fixed or discounted rate, charge an early repayment charge (ERC) if you overpay beyond an allowed limit. This calculator does not know your specific lender's rules — check your mortgage offer or lender terms before making a large overpayment.
What happens when you overpay?
Most UK lenders let you choose whether an overpayment reduces your monthly payment (keeping the same term) or reduces your term (keeping the same monthly payment). This calculator assumes the second approach — your payment stays the same or increases, and the term shortens — since that's usually where the larger interest saving comes from.
Should you reduce the term or the payment?
This depends on your own priorities and circumstances — reducing the term usually saves more interest, while reducing the payment lowers your monthly outgoings. This calculator can't tell you which is right for you; it's a starting point for your own decision, not financial advice.
Frequently asked questions
How much can I overpay on my mortgage?
It depends entirely on your lender and mortgage product — commonly up to 10% of the outstanding balance per year without charge, but this varies. Check your mortgage agreement or ask your lender for your specific allowance.
Does overpaying reduce mortgage interest?
Yes. Interest is charged on your outstanding balance, so any overpayment that reduces that balance sooner reduces the total interest charged over the life of the mortgage.
Is it better to overpay monthly or make a lump sum?
Both reduce your balance and therefore your interest — a lump sum reduces it immediately, while regular monthly overpayments build up gradually. Which suits you better usually depends on whether you have savings available now or prefer to spread extra payments over time. This isn't something we can tell you definitively; it depends on your own circumstances.
Can I pay my mortgage off early?
Often, yes, subject to your lender's terms — but some mortgages charge an early repayment charge if you pay off more than the allowed overpayment limit, particularly during a fixed or discounted rate period. Check your mortgage agreement before making a large overpayment or full early repayment.
What happens if my interest rate changes?
This calculator assumes your entered interest rate stays constant for the full period shown. In reality, UK mortgage rates often change — for example when a fixed or discounted period ends — which would change your actual figures. Recalculate with your new rate whenever it changes.
Can my lender charge me for overpaying?
Some can, if you overpay beyond their allowed limit — this is called an early repayment charge (ERC). Rules vary significantly by lender and product, so check your own mortgage terms before making a large overpayment.
How accurate is this calculator?
It uses a standard month-by-month mortgage calculation based on the figures you enter, assuming a constant interest rate and no fees or early repayment charges. It's a genuine calculation, not a rough estimate — but it can't account for your specific lender's rules, so treat the result as guidance rather than a guarantee.
How is the mortgage-free date calculated?
It's calculated by adding the estimated number of remaining months to today's date, based on a month-by-month simulation of your mortgage using the balance, rate and payment you've entered.