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Offset Mortgage Calculators

See how your savings could lower your monthly payments or shorten your mortgage term

Home Mortgage Calculators Offset Mortgage Calculators
Pete Mugleston

Author: Pete Mugleston

CeMAP Mortgage Advisor, MD

Updated: August 12, 2025

An offset mortgage can reduce the interest you pay by linking your savings to your mortgage balance.

Use our calculator to see how much you could save on interest and how it compares to a standard repayment mortgage. Enter your details to explore potential savings, with differences highlighted in green for clarity.

calculator icon

Offset Mortgage Calculator

This calculator shows you how your mortgage payments could look if you choose an offset mortgage and how much you could potentially save with this product type.

The total amount you're borrowing
£
Enter the mortgage rate, 5.5% is a typical rate currently but this can vary
%
Enter the mortgage term, 25 years is the average but lenders can offer shorter and longer terms
years
Enter an amount in pound sterling
£
Savings amount must be less than the loan amount

Without offset savings:

Monthly repayments:

Total cost:

With offset savings:

Monthly repayments:

Total cost:

Now that you have a rough idea of how much you could save on interest by offsetting your mortgage, you should speak to a specialist broker for bespoke advice about offset mortgages and access to the best deals that you qualify for.

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How an offset mortgage works

Offset mortgages links your savings and sometimes your current account to your mortgage balance. Instead of earning interest on your savings, the funds are used to offset the amount of your mortgage on which interest is charged.

For example, if you have a £200,000 mortgage and £20,000 in savings, you’ll only pay interest on £180,000. This can significantly reduce your monthly payments or help you repay your mortgage faster.

The advantage of an offset mortgage is its flexibility. You can still access your savings if needed, making it ideal for those who want to maintain liquidity while reducing their mortgage costs.

How our calculator works

An offset mortgage calculator can help you determine how much you could save on your interest payments by choosing this variety of mortgages over another product type.

With an offset mortgage, the amount you have in the offset savings account is deducted from the mortgage balance, and interest is only payable based on the difference between the two amounts. This calculator takes that into account and presents you with two sets of mortgage repayment results: one with offset savings and another for a standard repayment mortgage.

The results are based on the amount you’re borrowing, the savings you’re planning to offset, the mortgage term length, and the interest rate you enter. The two sets of results illustrate how much your mortgage could cost each month and how they compare overall.

The results are illustrative, and the actual amount you can borrow and how you repay will depend on your circumstances.

Are the calculations any different for interest-only mortgages?

For an interest-only offset mortgage, subtract your savings from the mortgage loan amount and work out how much interest would be due on the remaining figure.

You can enter this amount into our mortgage repayment calculator below and convert the results into ‘interest-only’ to get a rough idea of your monthly repayments.

Mortgage Repayment Calculator

This calculator can tell you the monthly and overall cost of your mortgage, based on the loan amount, interest rate, and term length.

Enter the amount you're borrowing
£
Enter the mortgage rate, 5.5% is a typical rate currently but this can vary
%
Enter the mortgage term, 25 years is the average but lenders can offer shorter and longer terms
years

The monthly repayments on a mortgage would be:

Loan amount:
Monthly repayments:
Total to repay:
Total interest:

How interest-only mortgages work:

With an interest-only mortgage, you only pay the interest each month. The original loan amount (the principal) remains unchanged and must be repaid in full at the end of the mortgage term. This means lower monthly payments, but you'll need a repayment plan for the full loan amount.

To get exact numbers based on your specific income, outgoings, age and other info, you'll need to speak to one of our experts. Lending policies change regularly, so this is purely for illustrative purposes only, and is not tailored financial advice.

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Calculating your overpayments

Some offset mortgages come with flexible features such as the ability to make overpayments, as an additional monthly or a lump sum. To work out what your mortgage balance will look like with extra payments factored in, work out the difference between your mortgage loan and the amount of savings you’re offsetting, and run the results through the calculator below.

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.

What you should do next

Now that you’ve completed your calculations, your next step should be to speak to a broker specialising in offset mortgages to put that number crunching into perspective.

Remember, any mortgage calculator can only provide a rough estimate of your mortgage repayments. However, an offset mortgage specialist is best placed to provide bespoke calculations and advise you on how to act based on the numbers calculated for you.

Call 0330 818 7026 or make an enquiry with us today, and we’ll match you with a broker who specialises in offset mortgages for personalised calculations and access to every lender in this corner of the market.

FAQs

If you have the same amount in offset savings as your mortgage balance, you might think you’ll have no interest to pay each month, but that’s not how the calculations work.

This is due to the differences in how credit interest and debit interest are calculated. Credit interest is based on the number of days in the calendar month, while debit interest—such as mortgage interest charges—divides the year into 12 equal months.

This means there will likely be interest payments to factor into your calculations if you take out a 100% offset mortgage.

Yes. Whether you or a family member place savings into the offset account, the mortgage interest payments will still be based on the difference between the outstanding mortgage balance and the amount of savings in the offset account.

Calculators are great, but they don't tell you everything you need to know. If you'd prefer an expert advisor to help, fill this out!

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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