UK Mortgage Calculator
Calculate UK monthly mortgage repayments in GBP (£) with stamp duty land tax (SDLT) estimations.
UK Repayment Summary
Repayment, interest-only, and the SVR cliff
UK mortgages come in two repayment shapes. A repayment mortgage pays down capital and interest so the balance reaches zero at the end of the term. An interest-onlymortgage pays only the interest, leaving the full capital outstanding at the end — the monthly cost is much lower, but you need a credible plan to repay the whole sum, and lenders now require evidence of one. Interest-only is mostly confined to buy-to-let.
The deal structure is where costs hide. Most borrowers take a fixed or tracker rate for an initial period of two to five years, after which the loan reverts to the lender's standard variable rate, which is typically several percentage points higher. Letting that happen is one of the most expensive passive mistakes in UK personal finance, and remortgaging before the reversion date is close to free money. Watch arrangement fees too — a headline rate with a large product fee can cost more than a higher rate without one.
Two more UK specifics: Stamp Duty Land Tax applies above a threshold on a banded basis, with different rates for first-time buyers and additional properties, and affordability is assessed by stress-testing your finances against a materially higher rate than the one you are offered.
Frequently asked questions
How is a UK mortgage repayment calculated?
Monthly UK mortgage payments are calculated using loan amount, interest rate, and term length (e.g. 25 years).
How do UK mortgages differ from US ones?
UK mortgages are typically fixed for an initial period of two to five years and then revert to the lender's standard variable rate, rather than being fixed for the whole term. Borrowers therefore remortgage repeatedly. There is also no general tax deduction for mortgage interest on a main residence.
How much stamp duty will I pay?
Stamp Duty Land Tax in England and Northern Ireland is banded on the purchase price, with different thresholds for first-time buyers and a surcharge on additional properties and non-resident buyers. Scotland uses Land and Buildings Transaction Tax and Wales uses Land Transaction Tax, both with their own bands. Rates change at fiscal events, so check current thresholds.
What is an affordability stress test?
Lenders must check you could still afford repayments if rates rose materially, alongside detailed scrutiny of income and outgoings under the FCA's Mortgage Conduct of Business rules. This is why the amount you can borrow is often well below a simple income multiple.