Free UK Mortgage Calculator

How much could you save by overpaying your mortgage?

Enter your mortgage details and see exactly how much interest you'll save and how many years come off your term.

Works for repayment mortgages
Monthly or lump sum overpayments
Year-by-year breakdown

Mortgage Overpayment Calculator

Enter your current mortgage details and your planned overpayment

Your current mortgage
£
%
yrs
Your overpayment
£
On top of your normal monthly payment
Most lenders allow 10% per year penalty-free
Interest saved
—
Time saved
—
New payoff date
—
Without overpayment
Monthly payment—
Total interest—
Total repaid—
Mortgage-free date—
✓ With overpayment
Monthly payment—
Total interest—
Total repaid—
Mortgage-free date—
Year-by-year balance
Year Balance (standard) Balance (with overpayment) Saving so far
Note: This calculator assumes a fixed interest rate for the full term and that overpayments are applied immediately to the capital balance. Results are estimates — your actual savings may vary based on how your lender applies overpayments. Always check your mortgage terms for any early repayment charges before overpaying.

Why overpay your mortgage?

Every pound you overpay reduces your outstanding capital, which means less interest accumulates each month. On a typical £200,000 mortgage at 4.5%, overpaying just £200/month saves over £30,000 in interest and cuts 6 years from the term.

The 10% rule

Most UK lenders allow you to overpay up to 10% of your outstanding balance per year without an Early Repayment Charge (ERC). Always check your mortgage agreement or call your lender before making a large overpayment.

Lump sum vs monthly

A lump sum overpayment saves more interest overall because the capital reduction happens immediately. Monthly overpayments are more achievable for most households. Using both together gives the maximum benefit.

Overpay vs save?

If your mortgage rate is higher than the interest rate you'd earn in savings, overpaying wins mathematically. With current mortgage rates above most savings rates for many people, overpaying is often the better financial move — and it's risk-free.

Frequently asked questions

Will I be charged for overpaying my mortgage?
Most fixed-rate mortgage deals allow overpayments of up to 10% of the outstanding balance per year without penalty. If you exceed this, you may be charged an Early Repayment Charge (ERC), which can be significant. Tracker and variable rate mortgages often have no overpayment limits. Always check your specific mortgage terms before overpaying.
Should I reduce my monthly payment or shorten my term when I overpay?
When you make an overpayment, most lenders will give you the choice of either reducing your monthly payment (keeping the same term) or keeping the same monthly payment and shortening your term. Shortening the term saves more interest overall and clears your mortgage faster — this is what our calculator assumes. Ask your lender which option they apply by default.
Does overpaying affect my credit score?
Making mortgage overpayments will not negatively affect your credit score. In fact, reducing your overall debt level can have a positive effect over time. However, missing a regular mortgage payment — even if you have previously overpaid — can still damage your credit record.
Can I overpay an interest-only mortgage?
With an interest-only mortgage, your regular monthly payments only cover the interest — the capital balance never reduces. Any overpayment goes directly toward reducing the capital. This calculator shows the effect for repayment mortgages; interest-only overpayment savings work differently and depend heavily on your lender's terms.
Is it better to overpay my mortgage or invest the money?
This depends on your mortgage interest rate versus expected investment returns. Overpaying gives a guaranteed, risk-free return equal to your mortgage interest rate. Investing could return more over the long term, but carries risk. Many financial advisers suggest paying off high-interest debt first, and considering investment once mortgage rates are relatively low. A fee-only financial adviser can help you decide based on your specific situation.