UK mortgage overpayment calculator
Find out how much interest and time you could save by paying a little extra off your mortgage each month, or in one lump sum.
What overpaying does
Enter your balance, rate and years left to see the result.
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How overpaying a mortgage works
On a repayment mortgage, interest is charged on the balance you still owe. When you pay extra, the balance drops sooner, so every later month charges less interest. More of your normal payment then goes towards the balance, and the effect builds up over the years.
This calculator keeps your regular monthly payment the same and adds your overpayment on top. The saving comes from clearing the mortgage earlier, not from paying less each month.
Monthly overpayments and lump sums
A small monthly overpayment and a one-off lump sum both work, and you can combine them. A lump sum made now saves the most, because it starts reducing the balance straight away. Regular overpayments are easier to keep up and still add up to a large saving over a long mortgage.
Check your limit first
Many lenders let you overpay up to 10% of the balance a year without charge. Above that, an early repayment charge can wipe out the benefit, particularly on a fixed rate. Your mortgage terms and your lender will confirm your own limit and whether the overpayment shortens the term or lowers your monthly payment.
Overpaying is not always the best use of spare cash. If you have more expensive debts, or no emergency savings, those usually come first. A regulated mortgage adviser or a free service such as MoneyHelper can help you decide.
What this calculator assumes
- It is a repayment mortgage, not interest-only, and the rate stays the same for the whole term.
- Interest is worked out monthly on the balance. Lenders vary: some charge daily or yearly, so their figures can differ slightly.
- The overpayment reduces the balance and shortens the term, with your regular payment staying the same.
- Fees, early repayment charges and changes of rate are not included.
- The result is an estimate. Your lender can give you the exact figures.
Questions people ask
How much does a £200 monthly overpayment save?
On a £200,000 mortgage at 4.5% over 25 years, £200 extra a month saves tens of thousands of pounds in interest and cuts years off the term. Change the figures in the calculator above to see the result for your own mortgage.
Is it better to overpay or save the money?
It depends on the rate. Overpaying earns you your mortgage rate, tax free, because you avoid that interest. If you can earn more than your mortgage rate after tax on savings, saving may win, but savings rates can change and the money stays accessible. Keep an emergency fund before you overpay.
Will I get charged for overpaying?
Not usually, within your lender's yearly allowance, which is often 10% of the balance. Over that, you may pay an early repayment charge, especially during a fixed or discounted rate period. Check your mortgage offer or ask your lender.
Do overpayments lower my monthly payment or shorten the term?
That depends on your lender. Many shorten the term and leave the monthly payment unchanged, which saves the most interest. Some lower the payment instead. Ask your lender how they apply it, and ask them to shorten the term if you want the biggest saving.
Is what I type stored or shared?
No. The calculation runs in your browser and nothing you enter is sent to us. Our privacy page has the details.
Is this financial advice?
No. It gives an estimate for information only. For advice on your own mortgage, speak to your lender or a regulated mortgage adviser.