How to Use Our Remortgage Calculator

Remortgaging is when you switch your mortgage to a new lender or product before your current deal ends—typically because interest rates have dropped, you want a better deal, or you're coming to the end of a fixed-rate term. The moment you decide to explore switching, the remortgage calculator becomes essential. It answers the question that matters: will I save money, and is it worth the fees?

Your current mortgage might be costing you £1,100 a month, and you've spotted a new rate that's 0.5% lower. But switching involves early repayment charges, product fees, and the cost of the application process. The remortgage calculator lets you plug in both sets of numbers—old deal and new deal—and see the real bottom line. Not the headline rate the marketing emphasizes. Not the monthly saving before fees. The actual total saving after all costs are deducted.

Under FCA MCOB 7 rules, lenders must disclose early repayment charges and product fees upfront. The Bank of England's interest rate moves every six weeks, and mortgage headlines track it closely. But your personal decision—to switch or stay—is made with real numbers from the calculator.

How to Use the Remortgage Calculator: Step by Step

Step 1: Gather your current mortgage details

Before you open the calculator, pull your mortgage paperwork. You'll need:

The original loan amount (principal)
The interest rate you're currently paying (e.g., 4.8%)
How many years you've paid so far (or how many months remain)
The total term of your mortgage (e.g., 25 years)
Any early repayment charge for breaking the deal early

Contact your lender for the early repayment charge—it's usually a percentage of your remaining balance (1–3%) or a flat fee. This is often the hidden cost that swings the entire decision.

Step 2: Find your new mortgage offer

Get quotes from at least three lenders. You're looking for the interest rate, the product fee (if any), the term length, and how long the fixed rate lasts. Don't just copy the headline. A rate 0.5% lower but with a £2,000 product fee might be worse than a slightly higher rate with no fee.

Step 3: Enter your current deal

The calculator has two sections: "Your current mortgage" and "Your new offer." Start with your current one.

Remaining balance: the amount you still owe (on your mortgage statement)
Current interest rate: the percentage you're paying now
Years remaining: how long until your mortgage ends
Early repayment charge: the £ amount the lender quoted

The calculator shows you your current monthly payment and the total interest you'll pay until the end of the term.

Step 4: Enter your new offer

Now fill in the "Your new offer" section:

Remaining balance: this stays the same (same debt, different lender)
New interest rate: the rate you've been quoted
Years remaining: same as now (unless you're extending or shortening)
Product fee: the one-off fee the new lender charges (the calculator adds this to the loan balance)

Step 5: Review the comparison

The calculator shows you side-by-side figures: your old monthly payment versus your new monthly payment, the monthly saving, and the total saving over the whole remaining term. This total already accounts for the early repayment charge and product fee. It's the number that matters.

If the total is positive and large enough (typically £2,000+) to justify the effort, switching makes financial sense. If it's marginal (under £1,000), the effort might not be worth it.

Understanding Your Remortgage Calculator Results

The calculator gives you four headline figures. Here's what each means:

Monthly payment (current versus new)

On a £150,000 remaining balance at 4.8% over 20 years, you're paying roughly £791/month. If the new rate is 3.9%, your new payment drops to £720—a saving of £71 per month. That saving happens every month for the next 20 years, which compounds significantly.

Total interest over the remaining term

Your current deal will cost you [X] in total interest. The new one will cost you [Y]. The raw difference is your interest saving—before fees and early repayment charges. This is useful context, but it's not the full story.

Early repayment charge

This is the cost of breaking your current mortgage early. Lenders often quote it as a percentage of your remaining balance (e.g., 1% = £1,500 on £150,000). The calculator subtracts this from your saving.

Product fee

This is the lender's fee for setting up the new deal, typically £500–£1,500. If your new deal has no fee, brilliant. If it does, the calculator adds it to your loan balance, which means you'll pay interest on it too.

The net saving

At the bottom, you'll see your total saving or cost over the remaining term—everything combined. If it's positive and substantial, remortgaging makes sense. If it's marginal or negative, your current deal is probably fine.

Comparing Mortgage Deals: The Full Picture

The remortgage calculator compares rates and fees, but other factors matter too:

Product features: Is the new deal flexible (can you overpay without penalty)? Does it include a free valuation, free legal work, or a cashback offer? Some lenders cover the survey cost; others charge you £200–£500. The calculator won't catch these hidden benefits or costs.

Broker fees: Many brokers are free (paid by the lender), but some charge you. Add this to your comparison.

Timing: Remortgaging takes 8–12 weeks from application to completion. Are you locking the rate in now, or later? If rates are rising, locking in early is valuable. If they might fall, waiting could be better. The calculator doesn't predict rates—neither can you—so model a few scenarios.

Use our mortgage calculator to stress-test different rate scenarios. Ask "what if rates rise by 0.5%?" or "what if I overpay by £100/month?" Understanding how sensitive your payment is to small changes helps you decide if switching is worth the risk.

When Is Switching Worth the Cost?

Here's the honest bit: remortgaging isn't free, and not every saving is compelling.

If your early repayment charge and product fee total £2,000, and your monthly saving is £50, you need 40 months (just over 3 years) to break even. If you're planning to stay in your home for 5+ years, switching is almost always worth it. If you might move in 2 years, it probably isn't.

Find your break-even point: the number of months until your monthly savings add up to your switching costs. If that's 2 years or less, switch. If it's 3–5 years, it depends on your certainty about staying. If it's more than 5 years, ask yourself how confident you are you'll be there that long.

Lenders' incentive is to make remortgaging sound like a no-brainer. Often, it isn't. The calculator removes emotion from the picture. Use it, and don't just trust the marketing.

Consider using our mortgage payoff calculator to explore overpayment scenarios too. If your new rate is only marginally better, but the flexibility to overpay is higher, that changes the whole picture. Overpaying by £100/month can save you years of mortgage and tens of thousands in interest.

Frequently Asked Questions

How accurate is the remortgage calculator?

Very accurate for standard mortgages. It uses the standard amortisation formula and handles fixed rates correctly. It won't capture edge cases (unusual mortgage terms, commercial mortgages, or non-standard lenders). Use the calculator as a starting point and confirm exact figures with your lender before committing. Remember: early repayment charges and product fees vary by lender and your circumstances.

What if I don't know my exact remaining balance?

Check your latest mortgage statement—it shows the outstanding balance clearly. Or call your lender. You can usually request a redemption figure (the exact amount to pay off the mortgage on a specific date), which includes a few days of accrued interest. Use the redemption figure if you're planning to remortgage within the month.

What if interest rates drop after I fix my new rate?

Remortgaging locks you into a new rate for a fixed period (e.g., 5 years). If rates fall further, you'll wish you'd waited. If rates rise, you'll be glad you switched. This is interest-rate risk. Model a few scenarios: what if rates rise by 1%? What if they fall by 1%? If your decision holds across all scenarios, you're on solid ground.

Can I include overpayments in the remortgage calculator?

Most remortgage calculators assume you pay the minimum only. But your new deal might allow overpayments without penalty. If it does, use our mortgage payoff calculator to model an extra £100/month and see the impact on your remaining term.

What if the numbers say I should switch, but it feels risky?

Numbers tell one story; risk tells another. If the saving is small (under £100/month) and you're uncomfortable with the process, don't switch. Peace of mind is worth something. But if the saving is substantial (£200+/month or £10,000+ over the term), it's usually worth the effort and risk. Use the calculator to set the baseline, then factor in your own comfort level.

Should I use a mortgage broker or apply directly?

Brokers are usually free—they're paid commission by the lender. They have access to products you might not find easily online and handle the paperwork. Direct lenders might offer small incentives to apply with them. The remortgage calculator works the same way either route. Compare the all-in cost (rate + fees) across at least three options, whether from brokers or direct.

What if my lender won't give me a quote because my situation has changed?

Lenders reassess your finances when you apply to remortgage. If your credit score has dropped, or you've taken on new debt, they might decline you or offer worse terms. The remortgage calculator assumes you get the rate you've been quoted. If you're unsure about affordability, run the numbers with a slightly higher interest rate to stress-test your budget.

Next Steps

Open our remortgage calculator right now. It takes less than a minute to see whether switching makes financial sense. Plug in your current deal, your new offer, and let the maths do the work. If the total saving is positive and substantial, book a call with your lender or broker. If it's marginal or negative, your current deal is probably fine.

If you're exploring a remortgage as part of a bigger financial picture—maybe you're also considering whether to overpay, or you're saving for a future move—use our calculators in combination. Start with the mortgage calculator to model how different terms affect your payment, then the remortgage calculator to compare specific deals, then the debt payoff calculator to work out how overpayments change your timeline. The full picture is worth the extra few minutes.