Remortgage Calculator

How the Remortgage Calculator works

This remortgage calculator compares your current monthly repayment with the estimated repayment on a new capital-and-interest mortgage. Enter your outstanding balance, current repayment, new interest rate and remaining term in years and months. You can then include a product fee and choose whether to add it to the mortgage or pay it upfront.

The main result shows whether the new estimated repayment is lower, higher or unchanged. Add up to two alternative deals to compare different rates, product fees and upfront switching costs using the same balance and remaining term.

If you want to explore repayments over different mortgage terms, use the Mortgage Calculator. This page holds the remaining term constant so the remortgage deals can be compared on the same basis.

What to enter

• Outstanding mortgage balance: the amount still owed on your mortgage.
• Current monthly repayment: your scheduled capital-and-interest payment, excluding insurance and voluntary overpayments.
• New interest rate: the annual rate for the deal you are considering.
• Remaining mortgage term: the years and months left to repay the mortgage, up to a maximum of 50 years.
• Product or arrangement fee: the fee for the new deal, if any.
• Other upfront switching costs: costs you expect to pay separately, without entering the product fee twice.

Product fee added to the mortgage or paid upfront

The way you pay a product fee affects both your estimated repayment and your initial switching costs. The calculator supports both treatments for your main deal and each comparison.

Product fee added to the mortgage

The fee is added to your outstanding balance before calculating the new repayment. You therefore borrow more, and the estimated repayment includes repayment of the fee and interest on that additional borrowing. The calculator does not also deduct the same fee as an upfront cost.

Any other upfront switching costs you enter remain separate initial costs. A financed product fee does not mean the deal has no cost; its cost is included in the mortgage repayment.

Product fee paid upfront

The new repayment is calculated using your outstanding mortgage balance without adding the product fee. The fee is instead combined with your other entered upfront switching costs when calculating payment savings over your chosen comparison period.

How the estimated monthly repayment is calculated

The calculator uses a standard repayment-mortgage formula with monthly interest. The annual interest rate is divided by 12, and the remaining term is converted into a whole number of months.

Monthly repayment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P: the balance used for the new mortgage, including the product fee if it is added to the mortgage.
• r: the annual interest rate divided by 100 and then by 12.
• n: the remaining term in months.

At a 0% interest rate, the estimated repayment is simply the balance used for the calculation divided by the remaining number of months.

Your lender’s figure may differ because of its interest calculation method, payment dates, rounding or mortgage terms. The calculator provides an estimate rather than a lender quotation.

Worked example: comparing a new deal with an upfront fee

Suppose your outstanding balance is £120,000, your remaining term is 10 years and your current repayment is £1,200 a month. You are considering a 0% illustrative rate, with a £1,000 product fee paid upfront and £200 of other upfront switching costs.

A 0% rate is used here to make every step easy to follow. It is an arithmetic illustration, not a suggestion that such a deal is available.

Outstanding balance	£120,000
Remaining term	10 years, or 120 months
Illustrative new interest rate	0%
Estimated new monthly repayment	£120,000 ÷ 120 = £1,000
Monthly saving	£1,200 − £1,000 = £200
Total upfront switching costs	£1,000 + £200 = £1,200
Upfront costs recovered	£1,200 ÷ £200 = 6 months
Payment savings after upfront costs over 2 years	(£200 × 24) − £1,200 = £3,600

If the £1,000 product fee were added to the mortgage instead, the balance used would be £121,000. At the same illustrative 0% rate over 120 months, the estimated repayment would be £1,008.33 a month. Only the £200 of other costs would be treated as upfront.

Choosing a comparison period

Monthly results do not require a comparison period. To see how payment differences accumulate after upfront costs, enter a period in years and months. It must be at least one month and cannot exceed your remaining mortgage term.

Choose a period during which the repayments and rates you have entered are a reasonable assumption for the comparison. For example, comparing payments over a deal’s fixed-rate period avoids assuming that its initial rate continues for the entire remaining mortgage term.

The calculator does not predict future rates or changes to your current repayment. If either repayment changes during the chosen period, the payment-savings estimate will no longer describe those changed circumstances.

Understanding the payment-savings chart

Each completed deal has its own line. The starting position is minus the upfront switching costs entered for that deal. Each subsequent month adds the difference between your current repayment and the estimated new repayment.

Payment savings after upfront costs = (current repayment − new repayment) × elapsed months − upfront switching costs

A positive value means lower payments have exceeded the entered upfront costs by that point. A negative value means the comparison still represents additional payment costs after allowing for those upfront costs.

This chart compares payment flow. It does not compare total mortgage costs, interest paid or outstanding balances at the end of the period. A lower monthly payment is therefore not, by itself, proof that a deal is cheaper overall.

When are upfront costs recovered?

Where a deal has upfront costs and a positive monthly saving, the calculator divides those costs by the unrounded monthly saving and rounds up to the next whole month. A recovery point is shown only if it falls within your selected comparison period.

Each deal is assessed separately. A deal with no entered upfront costs does not need a recovery marker. A deal with no monthly saving cannot recover upfront costs through lower payments under the assumptions entered.

Comparing remortgage deals fairly

A lower interest rate can come with a higher product fee, while a deal without a product fee can have a higher repayment. Comparing both repayments and switching costs helps you see that trade-off over the period that matters to you.

Keep the balance and remaining term the same when comparing rates and fees. Extending the term may reduce the monthly repayment while changing how long you remain in debt. Use the Mortgage Calculator to explore term changes separately.

If your aim is to repay the mortgage sooner, the Mortgage Overpayment Calculator can estimate the effect of regular additional payments. Voluntary overpayments are not included in this remortgage repayment comparison.

Other switching costs to consider

Check which costs apply to the actual deals you are comparing. Costs paid separately can be entered in the other upfront switching costs field.

• Early repayment charges on your existing mortgage.
• Mortgage exit or administration fees.
• Broker fees.
• Legal or conveyancing fees.
• Valuation fees.
• Other charges you expect to pay upfront when switching.

Do not enter a cost that the lender covers, and do not enter the product fee again if you have already included it in the product fee field. Cashback and other incentives are not modelled separately by this calculator.

What this calculator includes and excludes

The calculator includes:

• An estimated capital-and-interest repayment for the new deal.
• A remaining term entered in whole years and months.
• A product fee either added to the mortgage or paid upfront.
• Other upfront switching costs entered by you.
• Up to two independent alternative deals.
• Payment differences over an optional comparison period.

The calculator does not automatically include:

• Future interest-rate or repayment changes.
• Charges or fees you have not entered.
• Interest-only or part-interest-only mortgage structures.
• Additional borrowing beyond the entered product fee.
• Overpayments, payment holidays or missed payments.
• Cashback, savings interest or investment returns.
• Total-cost or outstanding-balance comparisons.
• Lender eligibility, credit checks or affordability assessment.

If you are exploring a larger borrowing amount, the Affordability Calculator provides illustrative income-multiplier scenarios. It does not establish whether a lender will approve that borrowing.

For a rental property, use the Rental Yield Calculator to examine rental income and running costs separately. Mortgage payment savings and rental yield measure different things.

Important note

This calculator provides general information, not financial advice or a mortgage offer. Check the lender’s repayment quotation, fee treatment, early repayment charges and deal conditions before making a decision.

Sources and review

The repayment estimate uses the standard monthly amortisation formula explained above. The worked example shows the calculation explicitly so its assumptions and figures can be checked. The external references below provide context on mortgage switching and fees; they do not validate this calculator’s individual results.

• Financial Conduct Authority — remortgaging without additional borrowing: regulatory context for switching mortgages and lender assessment.
• Nationwide — mortgage fees and charges: a lender-specific explanation of mortgage charges and the interest implications of adding a product fee to borrowing. Other lenders’ fees and conditions may differ.

For the charges and conditions that apply to your own mortgage, check your current lender’s redemption statement and the proposed lender’s mortgage illustration and fee schedule. These documents provide the relevant figures for your repayment, fee treatment and switching costs.

This calculator compares mortgage payments and entered upfront costs over your selected period. It does not compare total mortgage costs or outstanding balances, establish eligibility, recommend a deal or replace a lender quotation.