Mortgage Overpayment Calculator
See how regular or one-off mortgage overpayments could reduce the interest you pay and help you become mortgage-free sooner.
See what overpaying could save you
Enter your mortgage balance, interest rate, remaining term and planned overpayment to calculate your potential savings.
The amount you currently owe on your mortgage.
Your current annual mortgage interest rate.
How many years are left on your mortgage.
Extra amount you plan to pay every month.
Optional lump-sum payment made now.
What could mortgage overpayments do?
Mortgage overpayments reduce the outstanding balance you owe. Because future interest is calculated on a smaller balance, overpaying may reduce the total interest you pay and could help you repay your mortgage sooner.
A smaller outstanding balance can mean less interest is charged over the remaining mortgage term.
Regular overpayments can reduce the number of months needed to repay your mortgage.
Use the calculator to compare monthly overpayments, a one-off payment, or a combination of both.
How we estimate your mortgage savings
The calculator compares your mortgage repayment schedule with a second schedule that includes the overpayments you enter.
Calculate your normal repayment
We use your mortgage balance, annual interest rate and remaining term to estimate your normal monthly repayment.
Apply your overpayments
We then apply the monthly and one-off overpayments entered into the calculator to reduce the outstanding balance.
Compare both scenarios
We compare the estimated interest and repayment time in both scenarios to show how much interest and time could be saved.
What this estimate assumes
To keep the estimate clear and useful, the calculator uses a simplified repayment model. Your actual mortgage may work differently.
The calculation assumes the interest rate entered remains unchanged for the remaining mortgage term.
The calculation is designed for a standard capital-and-interest repayment mortgage rather than an interest-only mortgage.
Monthly overpayments are treated as additional payments towards the outstanding mortgage balance.
Early repayment charges, overpayment limits and other lender fees are not included in the estimate.
What difference could a £100 monthly overpayment make?
Here is an example using a £250,000 repayment mortgage with 25 years remaining and an interest rate of 4.2%.
This is an illustrative estimate using the assumptions described above. Actual mortgage repayments, interest and savings can differ depending on your lender and mortgage terms.
Mortgage overpayment FAQs
Common questions about making mortgage overpayments and using this calculator.
Do mortgage overpayments reduce interest?
Overpaying a repayment mortgage can reduce the outstanding balance sooner. This can reduce the amount of interest charged over the remaining mortgage term, depending on your mortgage rate and lender's terms.
Is it better to overpay monthly or make a lump-sum payment?
Both can reduce your mortgage balance. Paying money towards the balance earlier can generally reduce the amount on which future interest is calculated. Which option is appropriate for you will depend on your finances and your mortgage terms.
How much can I overpay on my mortgage?
Overpayment allowances vary between mortgages and lenders. Some mortgages allow a certain amount to be overpaid without an early repayment charge, while others have different restrictions. Check your mortgage agreement or ask your lender before making a large overpayment.
Can my lender charge me for overpaying?
Some mortgage products may have early repayment charges or limits on penalty-free overpayments. The calculator does not include these charges, so check your mortgage terms before making an overpayment.
What happens if my mortgage interest rate changes?
This calculator assumes the interest rate you enter stays the same throughout the remaining term. If your actual mortgage rate changes, your repayments, total interest and potential savings may also change.
Does this calculator work for interest-only mortgages?
No. This calculator is designed for a standard capital-and-interest repayment mortgage. Interest-only mortgages work differently, so the results should not be used to estimate an interest-only mortgage.
About this mortgage estimate
This calculator provides an illustrative estimate based on the information you enter. It is designed to help you understand the potential effect of mortgage overpayments.
The calculator models a standard capital-and-interest repayment mortgage using the balance, interest rate and remaining term entered.
View our methodology →Your lender may have overpayment limits, early repayment charges or other conditions that are not included in this estimate.
Important: This calculator is for general information and illustration only. It is not financial advice and does not replace information provided by your mortgage lender or a qualified financial professional.