UK Remortgage Calculator: Compare Deals & Save

How It Works

When your fixed-rate mortgage deal ends, your lender usually moves you onto its standard variable rate (SVR) — and broker surveys put typical SVRs at roughly 7–8.5% in late 2026, well above the best new fixed deals. Remortgaging means switching to a new deal, with your current lender or a new one, without moving home. This calculator compares the two deals on a like-for-like basis: the same outstanding balance, the same remaining term, and the same repayment method (capital and interest), so the only differences are the interest rate and the cost of switching.

Three numbers decide whether a switch is worth it. The first is the monthly saving — the difference between your current payment and the new one. The second is the switching cost: the early repayment charge (ERC) on your current deal plus the new deal's arrangement and other fees. The third is the break-even point — how many months of savings it takes to cover the switching cost. A switch only saves you money over your comparison period if the break-even point falls inside it.

The calculator also shows what happens beyond the monthly payment. A lower rate means more of each payment goes to capital, so your balance falls faster: after two years on the new deal in the example below, you owe £3,594 less than you would on the old one. And the total interest over the remaining term shows the full prize — often tens of thousands of pounds — though that figure assumes the new rate held for the whole term, which it will not: fixed deals last two, three or five years, after which you would remortgage again or move to the SVR.

Worked Example

Take a £200,000 mortgage with 20 years remaining, currently on a 7.5% SVR, switching to a 4.5% two-year fixed deal with a 2% ERC (£4,000) and £999 of fees. The current payment is £1,611.19 a month and the new payment is £1,265.30 a month — a saving of £345.89 a month. Over the two-year deal that is £8,301.30 of gross savings. Subtract the £4,999 switching cost and the net saving is £3,302.30, with a break-even of 15 months (£4,999 ÷ £345.89 = 14.45, rounded up).

The interest picture is even starker. Over the full 20-year term, the current deal would cost £186,684.73 in interest; the new rate would cost £103,671.70 — a saving of £83,013.03 if the rate held. Even inside the two-year comparison period, the interest paid falls from £29,347.44 to £17,451.71, and the balance after 24 months is £187,084.54 on the new deal versus £190,678.96 on the old one.

Assumptions

• Both deals use the same outstanding balance and remaining term, with capital-and-interest repayment and monthly payments. Interest-only mortgages are not covered.
• Rates are assumed fixed for the whole comparison period and, for the full-term interest figure, for the whole remaining term. In reality a fixed deal ends after two, three or five years and the rate then changes.
• The ERC is entered as a percentage of the outstanding balance, which is how most lenders charge it — typically 1–5%, often tiered (for example 5% in year one of a five-year fix falling to 1% in year five). It applies only inside the deal period; once you are on the SVR there is usually no ERC at all.
• Arrangement fees are typically £0–£2,000 (often £999); valuation and legal fees are often free on remortgage deals, with a typical total cost of £300–£1,500 excluding the ERC. Enter your actual figures from the deal you are comparing.
• No Stamp Duty Land Tax applies on a standard remortgage, because no property changes hands. The exception is a transfer of equity — adding someone to the title — which can trigger SDLT on their share.
• Overpayments, payment holidays, cashback and free legal or valuation offers are not included in the comparison.

The table below shows how the two-year net saving changes with the new deal's rate, holding everything else at the worked example (£200,000, 20 years, current rate 7.5%, switching cost £4,999):

Notice the last row: at a 6% new rate the monthly saving is still £178.32, but the two-year net saving is negative — the £4,999 switching cost takes 29 months to recover, longer than the deal itself. A cheaper monthly payment is not the same as a cheaper deal, which is exactly why the break-even figure matters.

How to Use This Calculator

Start with the figures from your current mortgage statement: the outstanding balance, the remaining term and your current rate. If your deal has already ended, your current rate is your lender's SVR — check your statement or your lender's website. Then enter the new deal's rate and length, the ERC from your current lender (your annual mortgage statement or lender should tell you the percentage and when it ends), and the new deal's fees.

The headline result is your monthly saving. Below it, the table shows the gross saving over your comparison period, the switching cost, the net saving, the break-even in months, and the balances and interest under each deal. Use the CSV download to keep a copy of the comparison, and run it again for each deal you are considering — a deal with a lower rate but a higher fee can easily lose to a slightly higher rate with no fee.

Tips and Practical Advice

Start the process three to six months before your current deal ends. Most lenders let you lock in a new rate up to six months ahead, and many let you switch to a better rate if one appears before completion — so an early start costs you nothing and protects you from rate rises. If your ERC is large, check exactly when it ends: waiting a few months for it to fall to zero can be worth more than the saving from switching early.

Compare the total cost over the deal period, not just the headline rate — a £999 fee on a two-year deal adds about £42 a month to the true cost. Check whether your new lender offers a free valuation and free legal work, which many remortgage deals do, and factor in any cashback. And do not extend your term to cut the payment without thinking it through: a longer term lowers the monthly figure but adds years of interest, which usually wipes out the saving.

Sources: GOV.UK guidance on Stamp Duty Land Tax (no SDLT on a remortgage with no transfer of ownership); FCA mortgage rule review (remortgaging with a new lender); broker surveys of lender SVRs and typical remortgage fees, checked 13 November 2026. Last reviewed: 13 November 2026.

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