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Abodewise

Remortgage Calculator

Use this remortgage calculator to compare staying on your current mortgage deal vs switching to a new deal. Enter your balance, rates, term and any fees, then choose how long you want to compare for.

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What type of mortgage is it?
Repayment pays off interest and the balance each month. Interest-only pays just the interest, and the balance is repaid separately.
Current deal
New deal
Stay on current
Monthly payment£1,375.77
Interest paid (period)£50,922.74
Principal repaid (period)£31,623.73
Balance after period£168,376.27
Switch to new deal
Monthly payment£1,265.30
Interest paid (period)£41,317.91
Principal repaid (period)£34,600.02
Balance after period£165,399.98
Fees (ERC + product fee)£999.00
Monthly difference
-£110.48
Interest difference
-£9,604.84
Balance difference
-£2,976.29
Cash paid difference
-£5,629.55
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How this remortgage calculator works

This calculator compares the costs of staying on your current deal vs switching to a new deal over a chosen time period.

  • It estimates the monthly payment for each deal (repayment or interest-only) and then totals up interest and payments over the comparison period.
  • It includes your one-off switching costs: product fee and early repayment charge (ERC).

The “difference” numbers show new deal minus current deal (so negative can mean you pay less on the new deal).

Example model
This box is a fixed sanity-check using the default example numbers. It does not change when you edit the calculator.
Mortgage typeRepayment
Current balance£200,000.00
Current rate5.5%
New rate4.5%
Current term remaining20 years
New term20 years
Comparison period5 years
Product fee£999.00
ERC£0.00
Example outputs
Monthly payment (current)£1,375.77
Monthly payment (new)£1,265.30
Cash paid difference (new − current)-£5,629.55
Interest difference (new − current)-£9,604.84
Mortgage warning

This is a guide only. Real remortgage decisions depend on lender fees, rate changes, your credit profile, and product terms.

Before switching, check ERCs and fees carefully and consider speaking to a qualified mortgage adviser.
How it works

This remortgage calculator compares your current deal to a proposed new deal over a chosen horizon (for example, the next 2–5 years). It models:

  • estimated monthly payment under each rate
  • estimated interest paid and balance movement over the comparison period
  • fees you explicitly enter (product fee and an optional ERC)

The “difference” values are calculated as new deal minus current deal, so a negative figure means the new deal is cheaper over the comparison period (based on your inputs).

Rates and thresholds

Last verified: 05/03/2026. Fees and ERC rules vary by lender and product; this calculator relies on the values you enter.

For a fair comparison, align the period with your decision point:

  • Comparison period: commonly matches the remaining fix period or the new fix period you’re considering.
  • Fees: include the new deal fee and any ERC you’d pay to exit early (if applicable).
  • Term: changing term changes monthly payments and balance; don’t compare a 15-year remaining term to a new 25-year term without noticing the trade-off.
Worked examples

Worked examples (rounded):

Example 1 — £200,000 balance, repayment, compare 5 years, fee £999

  • Current: 5.50% with 20 years remaining → monthly ≈ £1,375.77
  • New: 4.50% over 20 years → monthly ≈ £1,265.30
  • Estimated cash paid difference over 5y (new − current): −£5,629.55

Example 2 — £250,000 balance, repayment, switching early with ERC

  • Current: 6.00% with 15 years remaining → monthly ≈ £2,109.64
  • New: 4.50% over 25 years → monthly ≈ £1,389.58
  • Fee £999 + ERC £2,000 included in the new-deal cash cost
  • Estimated cash paid difference over 5y (new − current): −£40,204.65

Example 3 — Interest-only comparison (3 years)

  • £180,000 interest-only: 6.20% vs 4.90% over 3 years, with a £1,500 ERC
  • Estimated cash paid difference over 3y (new − current): −£5,520.00
Edge cases and exclusions
  • Not all costs included: valuation, legal, broker fees and other charges aren’t auto-added.
  • SVR/reversion: this doesn’t model future rate reversion; use a comparison period that matches what you’re deciding.
  • Balance and term changes: extending the term can make the new deal look cheaper monthly while increasing lifetime interest.
  • Porting: moving home and porting a mortgage isn’t modelled.
  • Overpayments: not included in the comparison; overpayments can change balances and cash costs.
Assumptions
  • This is a simplified comparison. Your lender’s exact figures may differ.
  • The interest rates are assumed to stay the same over the comparison period.
  • For repayment mortgages, payments are estimated using a standard amortisation model.
  • For interest-only mortgages, the balance is assumed not to reduce over the period.
  • It includes the product fee and ERC you enter, but does not include all possible fees (valuation, legal, broker, etc.).
Methodology

Stay on current: estimates monthly payment and totals over the comparison period using your current rate and remaining term.

Switch to new deal: estimates monthly payment and totals using the new rate and new term, plus adds your product fee and ERC.

Differences are calculated as new deal minus current deal.

What to do next
FAQ
What does the remortgage calculator compare, in plain terms?
It compares staying on your current deal with switching to a new deal over a period you choose, including estimated payments and interest for both.
Why does the remortgage calculator ask for a comparison period rather than the whole mortgage term?
Many people compare deals over a practical window, such as the length of a fix. The comparison period helps you focus on that window rather than lifetime totals.
How are the product fee and early repayment charge treated in this remortgage comparison?
They are included as one-off costs in the “switch to new deal” scenario. The calculator does not model other switching costs like legal fees unless you include them yourself.
What does a negative “cash paid difference (new − current)” mean on this page?
It means the new deal is estimated to cost less in cash paid over the comparison period, after including the one-off fees you entered.
Should the new mortgage term match my remaining term when using the remortgage calculator?
It depends on your plan. Keeping the term similar helps like-for-like comparisons, while extending the term can lower monthly payments but may increase interest.
Does the remortgage calculator account for rates changing after the deal ends?
No. It uses the rates you enter for the comparison period. If the period extends beyond a fixed rate, treat the result as an illustrative estimate.
Can I use this remortgage calculator for an interest-only mortgage?
Yes. You can switch the mortgage type and the calculator will estimate payments accordingly, but it does not model repayment vehicles or lender-specific constraints.
What is a sensible way to interpret remortgage results before speaking to a broker?
Use it to get directional comparisons and identify the inputs that matter most (rate, fees, ERC, term). Then verify figures with lenders or an adviser.
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