Mortgage Overpayment Calculator
See how monthly overpayments can shorten your mortgage and save you thousands in interest. Change any of the numbers below to try different scenarios.
Your mortgage details
Start with the house you’re buying. The calculator works out how much you’d borrow and what you’d pay each month.
Agreed purchase price
10% deposit
Yearly rate, held for the whole term
Between 1 and 40 years
Monthly overpayment
Add extra each month to pay off your mortgage faster. Pick an amount or type your own.
Per month, on top of your payment
Mortgage timeline
How much you still owe, year by year. Move across the chart to compare.
Side by side
What changes when you overpay, from the first payment to the last.
| Measure | Without overpayment | With overpayment | Difference |
|---|---|---|---|
| Monthly payment | |||
| Mortgage term | |||
| Total interest | |||
| Total repaid |
For illustrative purposes only. Actual savings may vary. Consult your mortgage provider about overpayment limits.
How mortgage overpayments work
An overpayment is any extra money you pay towards your mortgage on top of your normal monthly payment. Interest is charged on what you still owe, so paying off some of the balance sooner means less interest in future. That can clear the mortgage earlier and reduce the total you pay.
What this calculator assumes
- A repayment mortgage, where each payment covers the interest and part of the balance.
- The same interest rate for the whole term, with interest worked out monthly.
- Your standard monthly payment stays the same, with the overpayment added on top every month.
- No arrangement fees, early repayment charges or changes in rate.
Limits to be aware of
Real mortgages are messier. Many deals move to a different rate after an initial fixed period, which changes your payments and the results. Many lenders only allow you to overpay up to a set amount each year without an early repayment charge. Going over that limit during a fixed or discounted period can trigger a charge, so check your own terms with your lender before you overpay.
The results are estimates for illustration only, not a quote or personalised financial advice. Before overpaying, it’s worth thinking about your emergency savings and any higher-interest debt (see Money Management).
Buying or remortgaging? Our guide to UK mortgages and buying a home explains deposits, Stamp Duty, affordability and re-mortgaging.
Want to talk it through?
Book a coaching session today to work through this mortgage calculator together.