Mortgage calculators
Explore how an extra monthly payment or a one-off lump sum could reduce the interest and remaining term of a repayment mortgage.
This is an illustration only. Check your mortgage's overpayment allowance and possible early repayment charges before making a payment.
View all mortgage calculatorsEnter your mortgage details to compare one overpayment scenario with your current repayment schedule.
Worked overpayment examples
Using the same formula as our interactive tool above, the table below compares how regular monthly overpayments and one-off lump-sum payments affect a £200,000 capital-and-interest repayment mortgage with 20 years (240 months) remaining at an assumed constant interest rate of 4.5%, where the normal contractual monthly payment (£1,265.30) is maintained.
| Overpayment scenario | Estimated interest saved | Estimated term reduction | Revised payoff term |
|---|---|---|---|
| Regular £100 / month overpayment | £12,949 | 2 yrs 3 mos (27 months) | 17 yrs 9 mos |
| Regular £200 / month overpayment | £22,936 | 4 yrs 0 mos (48 months) | 16 yrs 0 mos |
| One-off £10,000 lump sum overpayment | £13,746 | 1 yrs 6 mos (18 months) | 18 yrs 6 mos |
| One-off £20,000 lump sum overpayment (10% allowance illustration) | £25,934 | 3 yrs 0 mos (36 months) | 17 yrs 0 mos |
Illustrations assume interest is calculated monthly on the reduced balance, the interest rate remains constant for the full remaining term, and your lender reduces the remaining term rather than recalculating a lower monthly contractual payment. Always check your mortgage offer for annual overpayment limits and early repayment charges before making an overpayment.
A regular overpayment adds an extra amount to each scheduled payment, while a lump sum reduces the balance once. In both illustrations the contractual payment is maintained, so the potential benefit is lower interest and an earlier estimated payoff.
Repayment-mortgage interest is charged on the outstanding balance. Reducing that balance sooner can reduce later interest, but the result depends on how your lender calculates interest and applies the payment.
Overpayment allowances and early repayment charges are mortgage-specific. Check your mortgage offer or contact your lender before making an overpayment, or review our fixed vs variable mortgage guide and remortgage advice if your current deal is approaching its end.
You may wish to consider emergency savings, more expensive unsecured debt, pension and tax considerations, and access to cash. Anderson Reed Financial Services can help you understand the mortgage information to review, but cannot provide personal tax or pension advice.
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Questions about overpayments
An overpayment is an amount paid above your normal contractual mortgage payment.
It can reduce future interest by lowering the outstanding balance sooner, but lender calculations vary.
It can where the normal payment is maintained. This calculator uses that assumption.
It is a charge that may apply under your mortgage terms if you repay more than your allowance or repay early.
Some lenders allow overpayments of around 10% of the outstanding balance each year without an early repayment charge, but this is not universal and the rules can differ by mortgage and product. Check your mortgage offer or ask your lender.
A regular overpayment is added each month; a lump sum is applied once.
Lender treatment varies. This calculator assumes the contractual payment stays unchanged.
No. This calculator is for capital-and-interest repayment mortgages only.
Calculate each part separately and confirm how your lender applies overpayments.
No. It does not include fees, early repayment charges or lender allowances.
Continue exploring
Estimate how a mortgage amount, assumed interest rate and term could affect monthly repayments.
Use the repayment calculatorGet an income-based illustration of your potential borrowing range and property budget.
Use the borrowing calculatorEstimate property purchase tax in England or Northern Ireland, Scotland or Wales.
Use the Stamp Duty calculatorReturn to the calculator hub to see all available tools.
View all calculatorsAn overpayment illustration cannot check the terms of your current mortgage or whether an overpayment is right for your wider circumstances. Anderson Reed Financial Services can help you understand the mortgage information to review and the options available when your deal is approaching its end.
Your home may be repossessed if you do not keep up repayments on your mortgage.
Your property may be repossessed if you do not keep up repayments on your mortgage.
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Anderson Reed and Anderson Reed Financial Services are trading names of Anderson Reed Financial Services Ltd, an Appointed Representative of Connect IFA Ltd, which is authorised and regulated by the Financial Conduct Authority (Firm Reference Number 441505) and is entered on the Financial Services Register under reference 947349. The guidance and/or information contained within this website is subject to the UK regulatory regime and is therefore targeted at consumers based in the UK.
Your initial consultation is free and without obligation. We charge a fee for mortgage advice, and our standard fee is £695, payable only on formal application.
Commission disclosure: We are a credit broker and not a lender. We have access to an extensive range of lenders. Once we have assessed your needs, we will recommend a lender or lenders that provide suitable products to meet your personal circumstances and requirements, though you are not obliged to take our advice or recommendation. Whichever lender we introduce you to, we will typically receive commission from them after completion of the transaction. The amount of commission we receive will normally be a fixed percentage of the amount you borrow from the lender. Commission paid to us may vary in amount depending on the lender and product. The lenders we work with pay commission at different rates. However, the amount of commission that we receive from a lender does not have an effect on the amount that you pay to that lender under your credit agreement.
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