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Buying Budget

Remortgage Calculator

Estimate only

When a fixed or discounted deal ends, most borrowers move to the lender’s variable rate. This tool illustrates what a different rate and term could mean for your monthly payment and total interest, and how long a fee would take to pay for itself.

Assumed to be added to the new mortgage.

Illustrative monthly saving

£95.07

£1,289.58 now versus £1,194.51 on the illustrated deal.

Current payment

£1,289.58

New payment

£1,194.51

Break-even on fees

11 months

Interest on current deal

£129,499

Interest on new deal

£106,682

Total interest difference

£22,817

Things to be aware of

  • Actual remortgage products depend on your circumstances, property value and each lender's criteria. Early repayment charges on your current deal are not included.
  • Fees are assumed to be added to the new mortgage, so interest is charged on them.

Estimate only

Actual remortgage products depend on your circumstances, credit history, property value and each lender’s criteria. This illustration is not an offer and does not recommend any product or lender.
Explore budget trade-offs with AI

How this calculation works

Both payments use the standard repayment formula. The current payment is based on your balance, current rate and remaining term. The new payment adds any fees to the balance and uses the new rate and new term. Break-even divides the fees by the monthly saving.

current M = P · r₁ ÷ (1 − (1 + r₁)^−n₁)
new M = (P + fees) · r₂ ÷ (1 − (1 + r₂)^−n₂)
break-even months = ceil(fees ÷ (current M − new M))

Assumptions

  • Fees are added to the new mortgage rather than paid upfront.
  • Each rate is assumed to apply for the whole of its term.
  • No early repayment charge on the existing mortgage is included.

Limitations

  • Real deals usually have a short fixed period followed by a variable rate.
  • Eligibility depends on affordability, LTV and lender criteria at the time you apply.
  • Cashback, free valuations and free legals are not modelled.

Last reviewed: 1 September 2026 · Calculation version 1.0.0

Comparing a switch with the cost of staying

A simple fee break-even example

If a new deal reduces the monthly payment by £80 and switching costs total £1,200, the simple break-even point is 15 months. That only answers when payment savings recover fees. It does not compare remaining balances, future rates or the interest on fees added to the loan. A deal ending before the break-even point may not recover its upfront costs under those assumptions.

Keep the terms comparable

Compare offers over the same remaining term and balance before looking at the payment difference. Extending from 20 to 30 years can make the new payment much smaller without making the mortgage cheaper overall. Include product, valuation, legal and exit fees where relevant, plus any early repayment charge on your existing deal. A fee-free product may have a higher rate but a lower total cost over a short fixed period.

A switch still needs checks

Moving lender usually involves affordability and property checks. A product transfer with your existing lender may work differently, but availability and eligibility are lender-specific. Lower LTV can help with product choice, while a lower valuation can work against it. Keep dates of your current deal, offer expiry and any early repayment charge visible so a quoted saving is not defeated by the timing.

Further reading: MoneyHelper — remortgaging to get a better deal. Examples are illustrations using stated inputs, not quotes or personal recommendations.

See our method and limitations or report a correction.

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