Mortgage Increase Calculator
See what happens to a repayment mortgage when the interest rate changes: the new monthly payment, the cash increase each month and the extra cost over a year.
What a rate rise does to your mortgage
When a fixed-rate deal ends, or a tracker follows Bank Rate upwards, the same balance has to be repaid at a higher monthly rate. This calculator compares the standard repayment formula at two rates so you can budget for the change before your deal ends.
On £160,000 with 20 years left, a rise from 2% to 5.5% changes the estimated payment from about £809 to £1,100 a month - around £291 extra each month or £3,492 a year. Your lender's figure may differ slightly because it may use daily interest, exact dates, fees or a different remaining term.
Before your fixed rate ends
- Check the exact balance and remaining term on your latest mortgage statement.
- Run a few rates, not just one. A cautious stress test helps you see whether your household budget has room.
- Allow for product fees, early repayment charges and the possibility that rates move again.
- Speak to your lender or a regulated mortgage adviser for an illustration. This page is a planning tool, not a lending decision.
For the effect of making extra payments instead, try the mortgage overpayment calculator. For a fresh borrowing estimate, use how much can I borrow?. The MoneyHelper guide to mortgages is a useful impartial starting point.
How the estimate is calculated
For each rate, the calculator uses the capital-and-interest repayment formula with monthly interest and the number of months you enter. It assumes one fixed rate for the remaining term, no fees, no overpayments and no payment holidays. Interest-only mortgages need a different comparison and are not included here.
Frequently asked questions
Will my mortgage payment definitely rise by this amount?
No. This is an estimate based on the balance, term and two fixed rates you enter. Your lender may calculate interest daily, round at different stages, include fees or offer a different rate, so use the result for budgeting rather than as a formal quote.
Should I use my original mortgage amount?
No. Use the outstanding balance and the years remaining, both from your latest statement. Using the original figures will usually overstate the payment change after several years of repayments.
What if I have a tracker mortgage?
Enter your current rate and the rate you want to stress-test. A tracker rate may move again, so try several higher and lower scenarios rather than treating one result as a forecast.
Can overpayments reduce the impact of a rate rise?
They can reduce the balance on which interest is charged, but check your deal limits and early repayment charge first. Our overpayment calculator shows the potential interest and time saving.