UK Mortgage Calculator

A UK mortgage follows a few conventions that are quite different from the American model, and they shape every figure a lender or broker quotes you: the split between repayment and interest-only, short initial deals that revert to a variable rate, and pricing that steps down as your deposit grows. Knowing these before you apply makes the numbers make sense.

Repayment vs interest-only

Almost all UK residential borrowers take a repayment (capital-and-interest) mortgage, where every monthly payment clears some interest and some of the capital, so the balance reaches zero at the end of the term. That is what this calculator models. On an interest-only mortgage you pay just the interest and still owe the full capital at the end, which needs a separate repayment plan; today it is used mainly for buy-to-let.

Fixed deals, trackers and the SVR

UK mortgages are usually taken as an initial deal — most commonly a two- or five-year fixed rate, sometimes a tracker that follows the Bank of England base rate. When the deal ends you are moved onto the lender's Standard Variable Rate (SVR), which is typically much higher and can change at the lender's discretion. This is why most people remortgage to a fresh deal every few years rather than drift onto the SVR — see fixed vs variable rates.

Deposit, LTV and how the rate is priced

Your loan-to-value (LTV) is the loan as a percentage of the property value, so a bigger deposit means a lower LTV. Lenders price in bands — commonly 95%, 90%, 85%, 75% and 60% LTV — and each step down unlocks a cheaper rate. There is no PMI as in the US, but a small deposit simply costs more in interest. Getting under 90%, and ideally to 75%, makes a real difference to the monthly payment.

Affordability and stress testing

Since the mortgage market review, UK lenders assess affordability rather than lending on a simple income multiple. They check your income and outgoings and stress test whether you could still pay if rates rose. As a rough guide many will lend around four to four-and-a-half times income, but the real limit is what their affordability model allows. The affordability calculator gives you a sensible starting estimate.

Term length and overpayments

Twenty-five years is the traditional UK term, but 30- to 35-year terms are increasingly common to keep the monthly payment manageable — at the cost of more total interest. Most fixed deals let you overpay up to 10% of the balance each year without an early repayment charge, and because interest is charged on the outstanding balance, overpaying early saves the most and can shorten the term significantly. The payoff calculator shows the effect of paying more.

Stamp duty and the other costs of buying

Beyond the deposit, budget for Stamp Duty Land Tax (SDLT in England and Northern Ireland; Scotland and Wales run their own systems), plus conveyancing/solicitor fees, a valuation or survey, and any mortgage arrangement fee. These are one-off costs at purchase. Ongoing, council tax and buildings insurance are paid separately and are not bundled into the monthly mortgage as US escrow would be — so your true monthly housing cost is the repayment above plus those bills.