Mortgage Refinance Calculator

What this calculator does

This remortgage calculator compares your current mortgage against a new deal and shows whether switching is worth the cost. Enter your outstanding balance, current rate, and remaining term alongside the new rate, term, and any fees, and it returns the change in monthly repayment, the difference in total interest, and the break-even point.

In the UK the timing question matters more than in most markets, because deals typically fix for two to five years rather than the full term. Remortgaging is not an occasional opportunity here — it is a recurring event most borrowers face every few years.

When to use it

The standard trigger is your fixed deal approaching its end. Falling onto the standard variable rate is the outcome to avoid, and running your current rate against a realistic SVR figure shows exactly what that would cost. Start this calculation around six months out, which is when you can begin securing a new deal.

It is also the tool for deciding whether to exit a deal early. If rates have moved sharply you may save enough to justify an early repayment charge, but that is a calculation rather than an instinct — enter the charge as a fee and see whether break-even still lands somewhere sensible.

Understanding the inputs

Your outstanding balance is the current redemption figure, not the amount you originally borrowed. Remaining term should reflect what is actually left; comparing a fresh 25-year term against 18 years remaining is not like-for-like and will flatter the new deal.

Under fees, include the product or arrangement fee and any early repayment charge that applies. If you plan to add the product fee to the loan rather than pay it upfront, note that you will pay interest on it for the full term. Enter rates as quoted, and consider running the standard variable rate as a separate scenario.

How is this calculated?

Compare current monthly payment against new payment. Break-even = Closing Costs / Monthly Savings.

A worked example

Suppose you owe £240,000 at 5.75 percent with 21 years remaining, repaying about £1,637 a month. Your deal is ending and the SVR is 7.5 percent, which would push the repayment to roughly £1,905. A new five-year fix at 4.5 percent with a £999 fee brings it down to about £1,467.

Against the SVR that is a saving of £438 a month, and the fee is recovered in under three months. Against your current deal the saving is £170 a month with break-even at about six months. Both comparisons favour switching — but only the second is the honest one if your existing deal still has time left to run.

Limitations and assumptions

This calculator compares repayment mortgages on a principal and interest basis. It excludes buildings insurance, any ongoing fees, and the cost of borrowing additional funds. It assumes both mortgages are on a repayment basis and that the rate holds for the term entered.

Because most UK deals fix for two to five years, figures beyond your deal period are indicative rather than predictive. Interest-only and offset mortgages follow different arithmetic. Your lender's illustration, and a broker's view of the whole market, remain the authoritative sources before you commit.