Initial deal versus reversion
A fixed or discounted rate normally lasts for a defined period. Model the payment at the follow-on rate and shop ahead of the deal end rather than assuming the opening payment lasts for the term.
UK mortgage and purchase analysis
Model the fixed deal, reversion payment, SDLT, overpayments and interest-only exit plan.
Built for pounds sterling and UK mortgage conventions. It supports capital repayment, interest-only and part-and-part structures, with current England and Northern Ireland residential SDLT bands or a manual Scotland/Wales tax input.
Decision guide
How to evaluate a UK mortgage deal
The headline fixed rate is only the first layer. Compare completion cash, the balance at the end of the deal, the reversion payment, overpayment rules and the plan for every pound of interest-only capital.
Repayment structure
Capital repayment reduces the balance over time. Interest-only reduces the monthly mortgage payment but requires a credible, separately monitored way to repay the capital at maturity.
Completion cash
Deposit, transaction tax, product fee, conveyancing, survey and moving costs are separate cash needs. Adding a fee to the mortgage means paying interest on it.
Tax scope
The built-in SDLT bands are for residential purchases in England and Northern Ireland. Scotland uses LBTT and Wales uses LTT, so enter a verified manual amount for those jurisdictions.
Overpayment restrictions
Many products permit some penalty-free overpayment, but allowances and early repayment charges vary by deal and year. Use the mortgage offer as the authority.
Get regulated advice
This planning model does not assess eligibility or recommend a product. A regulated mortgage adviser or lender must consider income, commitments, credit, term and repayment strategy.
UK mortgage monthly repayment examples
Illustrative monthly payments on a 30-year loan at a constant 4.5% annual interest rate. The repayment column includes principal and interest; both columns exclude fees, insurance and future rate changes.
| Mortgage amount | Capital and interest repayment | Interest-only payment |
|---|---|---|
| £70,000.00 | £354.68 / month | £262.50 / month |
| £75,000.00 | £380.01 / month | £281.25 / month |
| £80,000.00 | £405.35 / month | £300.00 / month |
| £100,000.00 | £506.69 / month | £375.00 / month |
| £140,000.00 | £709.36 / month | £525.00 / month |
| £150,000.00 | £760.03 / month | £562.50 / month |
How to estimate an early repayment charge (ERC)
Some UK mortgage deals charge an ERC if you leave the deal early or pay more than the penalty-free allowance. Many lenders allow an annual overpayment of up to 10%, but the allowance, charge and calculation basis depend on your mortgage offer. For a simple illustration, a 2% charge applied to a full £200,000 balance would be £4,000. An excess overpayment may be charged on a different amount. Check your lender's terms and request an exact redemption figure before acting.
Interest-only versus capital repayment
For a constant rate, an approximate monthly interest-only payment is loan balance × annual rate ÷ 12. A capital repayment payment also reduces what you owe, while an interest-only payment generally leaves the original capital to repay at the end of the term. A part-and-part mortgage combines the two structures. The calculator above lets you compare those shares and model overpayments.
Its built-in SDLT estimate applies to residential purchases in England and Northern Ireland. Scotland and Wales use different property transaction taxes.
Plan with context
A UK mortgage comparison needs the payment, fees, LTV, and future rate risk.
The initial monthly figure is only the starting point. Deposit size, product period, arrangement fees, reversion rate, overpayments, and remaining balance determine the longer-term cost.
Deposit determines LTV
Loan-to-value compares the mortgage with the property price. Moving into a lower LTV band may change which products and rates are available.
Repayment versus interest-only
A repayment mortgage reduces principal over time. Interest-only payments leave the original capital to be repaid through a credible separate strategy.
Product rate versus reversion
A fixed or discounted introductory rate can end before the mortgage term. Model the lender's follow-on rate or a remortgage scenario rather than assuming the initial rate forever.
Fees can outweigh a lower rate
Arrangement, valuation, legal, booking, and broker charges should be compared over the period you expect to keep the product—not only through the advertised rate.
Overpayments need contract checks
Regular or lump-sum overpayments can reduce interest and term, but annual allowances and early repayment charges vary by lender and product.
Affordability is broader than the payment
Lenders assess income, commitments, dependants, credit, stress rates, and evidence. A calculator estimate is not an agreement in principle or mortgage offer.
Included
Property price, deposit, mortgage amount, repayment and interest-only estimates, term, rate, fees, LTV, overpayments, total interest, affordability context, and rate scenarios.
Not included
A lender's underwriting model, product eligibility, credit search, exact early repayment charges, tax, insurance, conveyancing advice, or a live mortgage offer.
Use it well
Compare illustrations on the same loan and product period, include every compulsory fee, stress the payment at a higher follow-on rate, and obtain regulated advice when appropriate.