Ditch Your Fix Calculator UK 2026

Q: What is an Early Repayment Charge (ERC)?

An Early Repayment Charge is a fee your lender charges if you leave a fixed-rate mortgage deal before it ends. It's usually a percentage of your outstanding balance — often 1–5%, typically stepping down each year of the fixed term. On a £200,000 balance a 2% ERC is £4,000, so it's a major factor in whether switching early makes sense.

Leaving a fixed-rate mortgage early usually triggers an Early Repayment Charge, typically 1–5% of the balance — often several thousand pounds. Whether switching is worth it depends on how much you would save at today's rates versus that charge. This calculator works out your break-even month and gives a clear verdict on ditching your fix.

Verdict

Total switching cost

—

Break-even point

—

New term

—

Long-term saving

—

👍 Pros of switching now

👎 Cons of switching now

Mortgage balance comparison

Current deal New deal ERC end Break-even

Zoomed: up to ERC end date

Should you ditch your fixed rate early?

When mortgage rates fall, borrowers still locked into a higher fixed deal face a tempting question: is it worth paying the Early Repayment Charge to jump onto a cheaper rate now? The answer hinges on three numbers — how much lower the new rate is, how long is left on your current fix, and the total cost of switching (the ERC plus valuation and legal fees).

This calculator settles it by finding your break-even point. It amortises both your current mortgage and the new deal — adding the switching costs onto the new balance, as most lenders do — while keeping your monthly payment the same. Each month it tallies the interest you'd save on the cheaper rate. The month that running total overtakes your switching cost is the moment the switch has paid for itself.

Reading the verdict

If you break even comfortably before your current fix ends, switching is usually worth serious consideration — and because you keep paying the same amount, the lower rate also shortens your term. If break-even lands after the ERC period, or the numbers never recover the cost, the calculator flags it clearly. Either way, treat this as a starting point and confirm the details with an FCA-regulated mortgage adviser before acting.

Your mortgage is secured debt and runs on its own schedule. For unsecured debts — credit cards, loans and overdrafts — see our debt snowball method guide and the rest of our debt payoff guides.

Frequently Asked Questions

What is an Early Repayment Charge (ERC)?

An ERC is a fee your lender charges if you leave a fixed-rate deal before it ends. It's usually a percentage of your outstanding balance — often 1–5%, typically stepping down each year. On a £200,000 balance a 2% ERC is £4,000.

Is it worth paying the ERC to switch to a lower rate?

It depends on how much lower the new rate is, how much time is left on your fix, and total switching cost. This calculator finds your break-even point — where cumulative interest savings exceed the switching cost. Break even well before your fix ends and it's usually worth considering.

How is the break-even point calculated?

The tool amortises both your current mortgage and the new deal (with switching costs added) using your existing monthly payment, comparing the interest paid each month. When the running total of interest saved exceeds the total switching cost, you've broken even.

What happens when my fixed-rate mortgage deal ends?

When your fixed-rate deal ends you are automatically moved onto your lender's Standard Variable Rate (SVR), which is usually much higher than the fix and can change at any time. To avoid the jump you can remortgage to a new deal or take a product transfer with your existing lender, ideally lined up before the fix expires.

When should I start looking for a new mortgage before my fix ends?

Start looking around six months before your fixed rate ends. A mortgage offer is typically valid for three to six months, so you can lock in a new deal early and have it ready to complete the day your current fix expires — avoiding any time on the lender's Standard Variable Rate. There is usually no obligation to proceed if rates improve.

Should I get advice before ditching my fix?

Yes. This calculator is indicative only and uses generalised amortisation rules. Your exact ERC, product fees and eligibility depend on your lender. Always speak to a qualified, FCA-regulated mortgage adviser before deciding.

Disclaimer: This calculator is indicative only and based on generalised amortisation rules. It does not constitute financial or mortgage advice. Your actual ERC, fees and eligibility depend on your lender and circumstances. Always consult a qualified, FCA-regulated mortgage adviser before making any decision about your mortgage.

How this calculator works

The method

It compares two futures for the rest of your current fixed period: staying on your existing rate, versus paying the Early Repayment Charge (ERC) now and switching to a new rate today. For each option it amortizes your mortgage month by month — interest on the balance plus your monthly payment — and totals the cost, including the ERC and any new-deal fees. The break-even month is the point where switching becomes cheaper than staying; before it, you are still recovering the ERC.

Assumptions & limitations

It uses the balance, rates, remaining fixed term and charges you enter; your exact ERC and rate come from your own mortgage illustration (ESIS).
It assumes each rate holds for the compared period and does not predict future Bank of England base-rate moves.
It excludes valuation, legal and broker costs unless you include them in the fees you enter.

Data sources

Every calculation runs in your browser on the balances and rates you enter, so the results reflect your own figures. Where we cite external data we use MoneyHelper — remortgaging and Bank of England — effective interest rates. Figures and rules change over time — always check the original source.

Built and reviewed by a UK Chartered Mechanical Engineer. More on our methodology.

In depth · Updated 2 Oct 2026 · 5 min read

How to calculate a mortgage early repayment charge (ERC)

An early repayment charge (ERC) is what your lender charges if you repay more than your allowance, or leave the deal, before your fixed or discounted rate ends. Working it out takes one line of maths — the harder part is comparing it fairly against the interest you'd save.

How an ERC is calculated

ERC = amount repaid early × the ERC percentage for the current year of your deal.

The percentage is set out in your mortgage offer and Key Facts Illustration (or European Standardised Information Sheet). It usually steps down as the deal goes on. A five-year fix might charge, for example, 5% in year one, 4% in year two, 3% in year three, 2% in year four and 1% in year five. Leave in year three with £200,000 outstanding and the ERC would be £200,000 × 3% = £6,000.

ERC vs exit fee: two different charges

Early repayment charge — a percentage of the balance, charged only if you leave or overpay beyond your allowance during the deal period. Often thousands of pounds.
Exit fee (sometimes called a mortgage exit or closure fee) — a smaller, fixed administration charge for closing the account, usually payable whenever you repay the mortgage, including at the end of the deal. Check your offer for both.

Ways to reduce or avoid the charge

Use your overpayment allowance. Many lenders let you overpay up to around 10% of the balance each year without an ERC.
Wait for a cheaper year. If the percentage is about to step down, a few months' wait can cut the charge by a third or more.
Port the mortgage. If you're moving home, many deals can be transferred to the new property without an ERC, subject to the lender's approval.
Lock in a new deal early. Most lenders let you arrange a product transfer or remortgage a few months before your fix ends, to start the day the ERC period expires.

Is it worth paying? Compare interest, not payments

The right comparison is the interest you'd save over the rest of your fixed period against the ERC plus any new fees — not the drop in your monthly payment. On £200,000 with 25 years left, moving from 5.5% to 4.2% lowers the payment by about £150 a month, but the interest saving is larger: roughly £2,590 over 12 months and about £5,170 over 24 months. Against a £6,000 ERC, that switch wouldn't pay for itself within two years — before counting arrangement fees.

That's exactly the sum this calculator runs on your own figures, including the break-even month. Remember that rates for your next deal aren't known today, so a switch that only just breaks even near the end of your fix is rarely worth the risk.

Written by Peter Barclay, UK Chartered Mechanical Engineer. Worked examples are calculated with the same month-by-month amortisation our calculators use and are illustrative only — educational information, not financial advice.

Methodology & trust

Written and reviewed by Peter Barclay, a UK Chartered Mechanical Engineer — who builds and maintains these tools, pairing engineering-mathematics training with a focus on the mechanics of debt repayment. The calculators use standard amortization formulas and fixed repayment orders. Read our methodology or more about the author.

DebtSnowball is not a financial adviser and is not authorised or regulated by the FCA (Financial Conduct Authority). These tools are for education and information only, not financial advice. If you are struggling with debt, get free, impartial help from StepChange, National Debtline or Citizens Advice.

Last reviewed: October 2026 Spotted an error? Report it and we will fix it.

Ditch Your Fix Calculator