Guide · United Kingdom
How Mortgage Affordability Works in the UK (2026)
Last updated 2026-04-14 · Published 2026-01-10
Learn how UK lenders estimate how much you can borrow: income multiples, affordability tests, SDLT cash needs, and what to model before you apply. With a link to our free UK calculator.
What “affordability” means in practice
When people ask how much they can borrow, they usually mean the maximum loan a lender might offer after checking income, debts, deposit, and interest rate. In the UK, that process is governed by FCA rules on responsible lending and each lender’s own credit policy. No blog article—and no free calculator—can replace a Decision in Principle from an FCA-authorised firm, but you can still learn the moving parts so conversations with a broker feel less opaque.
Most high-street lenders combine a simple income multiple (for example three to four and a half times salary for some borrowers) with a payment-based test: they check that your mortgage payment plus other committed costs stays within a sustainable share of gross income. Self-employed borrowers, bonus-heavy earners, or portfolio landlords face extra layers that a generic model cannot fully capture.
Income, debts, and what lenders haircut
Lenders start with provable gross income: payslips, tax returns, or SA302s for the self-employed. Variable income is often discounted—bonuses might only count at 50%, and overtime may be excluded unless it is stable across two or more years. Monthly commitments such as car finance, credit cards (often using a percentage of the limit, not the balance), student loans, and childcare reduce the income available for a mortgage payment.
When you use our UK mortgage calculator, enter those debts honestly in the monthly obligations field. The closer your inputs are to what will appear on a lender fact-find, the more useful your rehearsal numbers will be.
Deposit, LTV, and stamp duty cash
Your loan-to-value (LTV) ratio is the loan divided by the purchase price or valuation, whichever is lower. A lower LTV usually unlocks better rates and can offset a slightly stretched income multiple. Remember that deposit is not your only upfront cost: in England and Northern Ireland, Stamp Duty Land Tax (SDLT) can be a material line item, with first-time buyer relief on qualifying purchases.
Our calculator includes SDLT-style estimates for planning. Always confirm tax with your conveyancer because reliefs, additional-property surcharges, and regional regimes (Scotland LBTT, Wales LTT) differ.
Interest rates and future payment shocks
Affordability is not calculated only at your initial fixed rate. Lenders apply an interest rate “stress” so they can see whether you could still afford payments if rates rise at remortgage. The exact stress rate is internal to each lender but is typically above the pay rate you see advertised.
In GetMortgageCalc you choose the rate to model. Try both your expected product rate and a higher stress rate to see how sensitive your maximum borrowing is to payment changes.
Worked example (illustrative numbers only)
Suppose a household earns £65,000 a year gross, pays £350 a month in car and credit commitments, and has a 15% deposit on a £320,000 purchase. A lender might first translate income to a monthly gross figure, subtract obligations, and then solve for the loan amount that keeps housing costs within policy. Your actual offer could be higher or lower depending on credit score, probation, property type, and lender appetite.
Use the scenario fields in our free UK mortgage calculator to mirror your own numbers and export a PDF summary to discuss with an adviser.
Try the numbers yourself
Put your income, debts, rate, and term into our browser-only calculator for United Kingdom. No signup required.
Go to calculator →Frequently asked questions
Is an online affordability figure a mortgage offer?
No. Only an FCA-authorised lender or appointed representative can make a formal offer after underwriting. Calculators help you rehearse budgets and questions for that process.
Why might my broker’s maximum loan be lower than a calculator?
Brokers apply lender-specific scorecards, living-cost benchmarks, and stress rates. They may also exclude income you hoped would count. That gap is normal—use it to adjust expectations early.
Does GetMortgageCalc store what I type?
Calculations run in your browser; we do not operate a mortgage application database for your inputs in this app. See the privacy policy for analytics notes.
Where can I model SDLT alongside borrowing?
Open the UK calculator linked below and switch between affordability and repayment modes while reviewing stamp duty assumptions in the results panel.
Educational content only—not mortgage, tax, or legal advice. Confirm any decision with a licensed professional in your jurisdiction.