Updated: September 22, 2025
Mortgage Overpayments Calculator
Want to know how overpaying can alter the loan term and interest on your mortgage? Use our calculator below to find out how this all works.
Written by Pete Mugleston
Mortgage Expert, MD
If you’re considering making overpayments on your mortgage, use our calculator below to see exactly how much interest you could save and how this could affect the remaining loan term.
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.
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.
The following topics are covered below...
Why use this mortgage overpayments calculator?
The calculations for exactly what effect an overpayment on your mortgage will have can be nigh on impossible if you’re trying to do it manually. Our calculator will do all the hard work for you in seconds.
So, immediately, you’ll be able to see the impact your overpayments could have and, from there, can decide whether this is something you want to move forward with. No personal details are required. All you need to input is the following:
- 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 our calculator will do the rest – all simple! You’ll now see your new monthly repayment and an illustration showing how the loan term and potential interest savings could change.
If you’re still unsure of the amounts you wish to overpay by – whether this will be a lump sum or by increasing your monthly payments – you can re-input using different figures as many times as you wish until you reach an outcome that fits your requirements.
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How to calculate overpayments on an interest-only mortgage
The above calculator is aimed at assisting anyone with a capital and repayment mortgage only.
For interest-only mortgages, the amount of capital you owe remains the same throughout the term, so if you were to overpay the interest element, nothing would really change.
The best way to reduce your mortgage term and/or the amount of interest you pay is to review your repayment vehicle’s position and consider whether you can increase your investment in it so as to reach the target amount sooner than predicted.
If you’re unsure how this could work based on your circumstances, it would be best to speak with a mortgage broker who has experience with this type of repayment method.
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Why use Online Money Advisor?
Here’s how the mortgage brokers we work with will be able to help you decide whether overpaying on your mortgage is the right decision for you and, if so, how much this should be:
- Understanding how much you can overpay by. They’ll look at your existing mortgage lender’s terms and conditions to see exactly how much you can overpay and how this compares with other lenders.
- Budgeting for the right amount. Once you’ve decided you want to make an overpayment on your mortgage, your broker will review your finances so you can decide on an amount that will suit you best.
- Finding the right lender. If your existing lender’s overpayment terms don’t fit what you want to do, your mortgage broker will help identify those who can.
What you should do next
Our free, unique broker-matching service is designed to match you with the right mortgage broker who can meet your requirements – the first time! So get in touch or call us on 0330 822 0505, and we’ll ensure a mortgage overpayment specialist contacts you straight away to discuss this further.
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We know everyone's circumstances are different, that's why we work with mortgage brokers who are experts in all different mortgage subjects. Ask us a question and we'll get the best expert to help.
Written by Pete Mugleston
Mortgage Expert, MD
Pete, 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 found great success in going the extra mile to find mortgages for people whom many others considered lost causes. The experience he gained, coupled with 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 OMA of course!
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