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Mortgage Overpayment Calculator

Use our calculator to see how lump sum or monthly overpayments could reduce your mortgage interest and term.

Home Mortgage Calculators Mortgage Overpayment Calculator
Pete Mugleston

Author: Pete Mugleston

CeMAP Mortgage Advisor, MD

Updated: August 12, 2025

Overpaying your mortgage can reduce the total interest you pay, shorten your loan term, and help you own your home sooner.

Use our early mortgage overpayment calculator below to see the impact on your repayments, or speak to a trusted mortgage advisor to explore all your options.

Mortgage Overpayments Calculator

This calculator can show you how much you could save and what your new mortgage payments will look like if you were to make overpayments as a lump sum, monthly amount or both.

Estimate if not known
£
Years and months
Enter a percentage
%
An amount in pound sterling
£
An amount in pound sterling
£
Overpayment must be less than outstanding balance

Your current monthly repayment is:

What your mortgage repayments will look like based on your overpayments:

Potential mortgage term reduction:

Amount of interest you could save:

Now that you have a rough idea of how overpayments will affect your mortgage deal, make an enquiry to speak to a broker for bespoke advice about whether this is the right option for you.

Before overpaying, speak to a mortgage advisor to explore whether remortgaging or an offset mortgage could save you more in the long run.

How to calculate your mortgage overpayments

It will be quite tricky, if not impossible, to work out how making overpayments will alter your mortgage loan on your own.

So, here are three simple steps to make this process much easier:

Work out exactly how much you can comfortably afford to overpay – whether as an increase to your monthly repayments or as a lump sum. If you’re looking to increase monthly repayments, be sure to review all of your outgoings so you can be confident the new amount is affordable

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How this overpayment calculator works

Our mortgage overpayment calculator is very simple to use.

All you need to do is input the following details:

  • The amount you owe on your mortgage
  • Remaining loan term
  • The current interest rate on your existing mortgage deal
  • The amount you wish to overpay by – either monthly and/or a lump sum

And that’s it! Our calculator will then show you your new monthly mortgage repayment (if increasing), how this could alter the loan term and the potential interest you could save.

If you’re not sure exactly how much you may wish to overpay, you can alter the figures for those amounts to see a range of different outcomes until you find one that best fits.

What you should do next

Before making overpayments on your mortgage, it’s essential to check with your lender to understand their terms:

  • Early repayment charges (ERCs): Some lenders limit how much you can overpay annually without penalties.
  • Overpayment flexibility: Not all mortgages allow overpayments, or they may have specific restrictions.
  • How payments are applied: Some lenders reduce future payments rather than shortening the loan term.

If early repayment charges apply, or if you’re unsure how much you can overpay, it’s important to carefully evaluate your options. Overpaying isn’t always the best strategy—remortgaging or an offset mortgage could save you more in the long run.

Using our broker-matching service, we can connect you with a mortgage expert who can review your options and confirm the best course of action for your situation.

If you contact us or call us on 0330 818 7026, we’ll ensure that an advisor with experience handling these types of requests contacts you immediately.

FAQs

Yes, it’s possible, but the key difference between an interest-only mortgage and capital and repayment is that the amount you owe will never reduce, so, in effect, overpaying only the interest amount won’t change a great deal in terms of your mortgage.

To still achieve the key benefits of reducing your term and/or the interest you pay overall, you should review your repayment vehicle and assess whether you can overpay to reach the target amount sooner and repay the capital owed.

Before overpaying, speak to a mortgage advisor to explore whether remortgaging or an offset mortgage could save you more in the long run.

Pete Mugleston

CeMAP Mortgage Advisor, MD

Pete, a CeMAP-qualified mortgage advisor and an expert in all things mortgages, cut his teeth right in the middle of the credit crunch. With plenty of people needing help and few mortgage providers lending, Pete successfully went the extra mile to find mortgages for people whom many others considered lost...

Pete, a CeMAP-qualified mortgage advisor and an expert in all things mortgages, cut his teeth right in the middle of the credit crunch. With plenty of people needing help and few mortgage providers lending, Pete successfully went the extra mile to find mortgages for people whom many others considered lost causes. The experience he gained and his love of helping people reach their goals led him to establish Online Mortgage Advisor, with one clear vision – to help as many customers as possible get the right advice, regardless of need or background.

Pete’s presence in the industry as the ‘go-to’ for specialist finance continues to grow, and he is regularly cited in and writes for both local and national press, as well as trade publications, with a regular column in Mortgage Introducer and being the exclusive mortgage expert for LOVEMoney. Pete also writes for Online Mortgage Advisor of course!

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