mortgage early repayment calculator -- nothing leaves your browser
Add a property and mortgage to get started
Go to the Mortgages tab to add a mortgage, or load a saved file.
Split/Equity Mode Active:
Set the owner's share (%) of each property's equity. E.g., if partner owns 50% of her property, set Owner Share = 50%.
New Property Purchase:
Uses each mortgage's Allowance (%). HSBC mode reads the fixed-period end from each loan's Expiry Date — no bands needed (a loan whose fix has ended, or a tracker, shows £0).
Payment Details
Combine into New Mortgage
Early Repayment Charge (ERC) Rules:
* Annual Overpayment Allowance (AOA): Typically 10% of outstanding balance
* Allowance renews annually on fixed-rate start date
* ERC applies only to amounts over the allowance
* ERC = 1% of overpaid amount x years remaining in fixed period (reducing daily)
* Maximum ERC: 5% of the overpayment amount (above allowance)
The key question: does acting now pay off? This tracks the ERC you'd pay against the interest you'd save, month by month — where the net benefit crosses zero is your break-even point.
Break-even: ERC paid vs interest saved (by action month)
Per-Property Analysis
Net benefit analysis for each property showing when remortgaging becomes profitable.
Total repayment cost over time (all mortgages)
ERC "Waste" by Repayment Month
Month
Total Balance
Total Interest
Total Principal
Total ERC
Monthly Savings
Net Benefit
Deposit Available
How much can you cut your monthly outgoings — and what does it cost in lifetime interest?
No mortgages yet
Add at least one mortgage on the Mortgages tab to use the re-term modeller.
Re-term / Remortgage
today
Live term: 20 years
Term
New monthly re-termed part
Total /mo all loans
Δ vs now
Total interest re-termed part
Extra interest vs do-nothing
Monthly payment vs extra lifetime interest
How to read this
Re-terming cuts your monthly outgoings but almost always costs more in total interest —
you owe for longer, and here you'd move the big loan above its current 4.39%. The number that
matters is Extra interest vs do-nothing: the true price of the lower monthly.
On a small balance a fee-free deal matters more than a headline rate. “Do-nothing” interest is the
closed-form remainder on each loan's current path; a lender quote rounding the term may differ ~1%.
All options compared
Every way to act — including remortgaging only one loan — ranked to suit your goal. Use the slider inside to pick your action date.
The table re-ranks and the BEST pick follows your goal.
sm.mortgage
A mortgage early repayment and remortgage calculator.
Enter your mortgage details to see your repayment schedule
Model early repayment scenarios and see the savings
Check early repayment charges (ERCs) against your savings
Compare remortgage options side by side
All calculations run in your browser — nothing is stored