01 / START WITH YOUR NUMBERS
How to use the remortgage calculator
Enter the mortgage you have
Use the current balance, annual interest rate and remaining term. Add your estimated property value to see the loan-to-value ratio.
Enter the deal you want to explore
Choose a new annual interest rate and term. The balance remains the same: this tool does not include extra borrowing or fees added to the mortgage.
Add the costs of switching
Enter the total upfront cost, including any product fee, legal costs or early repayment charge. The calculator compares payments and shows a simple fee-payback period where monthly payments fall.
02 / THE NUMBERS IN PRACTICE
A worked example
This comparison keeps a £200,000 balance and a 25-year term, changes annual interest from 6% to 4.5%, and includes £2,000 of upfront switching costs. A £300,000 property value is used for LTV.
£1,111.66
- Current monthly payment
- £1,288.60
- Loan to value
- 66.67%
- Upfront switching costs
- £2,000.00
- Current remaining repayments
- £386,580.84
- New repayments plus costs
- £335,499.49
- Full-term saving / extra cost (−)
- £51,081.35
Fixed illustration using the starting inputs, separate from the live calculator above. Displayed amounts are rounded.
Repayment mortgages, same balance, rates fixed for both full terms. Switching costs are paid upfront. No additional borrowing or fees added to the mortgage.
03 / UNDERSTAND YOUR RESULT
A lower payment does not always mean a cheaper mortgage
Extending the term spreads capital repayments across more months. That can reduce the payment even if the rate has not changed. It can also increase total interest. Compare the total remaining repayments as well as the monthly difference.
The full-term comparison assumes both rates remain fixed for their complete terms. Real deals may change sooner. It is not a comparison of two fixed-rate deal periods and does not predict the rate after either deal ends.
04 / UNDERSTAND YOUR RESULT
What the fee-payback figure tells you
The simple payback divides upfront costs by the monthly payment reduction and rounds up to a whole month. For £2,000 of costs and £100 less paid each month, that is 20 months. It measures when cash-flow reductions match the fee, not when the overall mortgage becomes cheaper.
Different repayment terms can leave different outstanding balances at that point. This tool does not use an equity-adjusted deal-period comparison. If there is no monthly reduction, it reports no payback from monthly savings. Review early repayment charges and actual deal terms before switching.
PLAIN ENGLISH, PLEASE
Remortgage glossary
The terms behind the inputs and results, explained without the guesswork.
- Remortgage
- Replacing an existing mortgage with a new mortgage arrangement.
- Remaining term
- The time left to repay the current balance under the schedule being compared.
- Switching costs
- Upfront costs you enter for changing the mortgage. They are not added to borrowing here.
- Monthly saving
- Current calculated payment minus the new calculated payment. A negative result means an increase.
- Fee payback
- Upfront costs divided by positive monthly payment savings, rounded up to whole months.
- LTV
- The current balance divided by the entered property value. A value above 100% indicates the balance exceeds that value.
BEHIND THE ESTIMATE
How the calculation works
We calculate two repayment schedules for the same balance using each annual rate divided by 12 and each term in months. New total repayments include the upfront switching costs; current repayments have no extra switching fee.
The full-term saving is the current remaining repayment total minus the new total including costs. A negative value represents an extra cost. Fees are not financed, interest rates do not change and the calculation excludes additional borrowing.
Sources and further reading
Examples use Switcha’s calculation model above. Supporting information and linked guidance checked on 10 September 2026.