About this calculator
UK lenders answer "how much can I borrow?" with two different tests, and the lower one wins. The first is the loan-to-income (LTI) multiple — the headline "4.5 times your salary" figure. The Bank of England's Financial Policy Committee caps the flow of lending at or above 4.5× income to 15% of new mortgages, which is why 4.5× is the default ceiling for most borrowers, with 5× or more reserved for higher earners, some professions and larger deposits.
The second test is the one that actually bites: an affordability assessment, required by the FCA's responsible-lending rules, that checks you could still pay if rates were higher than today's deal. Lenders each set their own stress rate — testing at the pay rate plus roughly 3 points is typical — and they deduct your committed outgoings (loans, car finance, credit cards, childcare) before deciding what payment you can carry. A household can pass the income multiple easily and still be offered less because the stress test, at a 7–8% notional rate, produces a smaller loan. This calculator runs both, on the same income, deposit and term, and tells you which is binding.
How to use it
- Enter your gross income (and a partner's, if you are buying together) and the income multiple — leave it at 4.5 unless a lender has quoted you more.
- Set the rate you expect to pay and the stress margin; the stressed rate is the pay rate plus the margin.
- Choose the share of gross income you could give to housing costs at that stressed rate, and subtract monthly committed outgoings — the remainder is the payment budget the stress test uses.
- Read the two limits: the maximum mortgage is the lower of the LTI figure and the stress-test figure; add your deposit for the maximum price.
- Use the table to see how the answer moves if lenders stress harder or more gently.
The formula
The stress loan inverts the standard repayment formula M = P × r(1 + r)^n ÷ ((1 + r)^n − 1): instead of solving for the payment M given a loan P, it solves for the largest P whose stressed payment fits the budget B. The budget itself is (gross income ÷ 12 × budget share) − committed monthly outgoings.
Worked example
A single buyer on £60,000 with a £30,000 deposit: the 4.5× multiple suggests £270,000. But a 35%-of-gross housing budget is £1,750 a month, and at a stressed rate of 7.50% (4.50% pay rate + 3 points) over 25 years that budget supports £236,809 — so the stress test binds and the maximum mortgage is £236,809, a maximum price of £266,809. At today's 4.50% pay rate the payment on that loan would be £1,316.26 a month, comfortably inside the budget; the lender is protecting against the rate being 7.50% instead.
Sources: Bank of England Financial Policy Committee loan-to-income flow limit (15% of new lending at or above 4.5× income) and FCA MCOB 11.6 affordability requirements; the stress margin is typical lender practice and is adjustable, as each lender sets its own. Last updated: October 2026.
Frequently asked questions
How many times my salary can I borrow in the UK?
Most lenders cap most borrowers at 4.5× gross income (4.5× joint income for couples). The Bank of England limits lending at or above 4.5× to 15% of a lender's new mortgages, so higher multiples — 5×, occasionally 5.5× — exist but are rationed to higher earners, certain professions and low loan-to-value cases. Whatever the multiple, the affordability stress test can still produce a lower offer.
What is the mortgage stress test?
An FCA-required affordability check: the lender models your payment at a rate above your deal rate — commonly around 3 points higher, or a notional rate in the 7–9% range — and checks it fits your budget after essential and committed spending. It exists so a rate rise does not immediately make the loan unpayable. This calculator's stress margin defaults to +3 points and is adjustable, because each lender sets its own.
Do debts and outgoings really reduce how much I can borrow?
Yes — committed outgoings are subtracted before the payment budget is set. A £300-a-month car payment can cut the stress-tested maximum by roughly £40,000 at typical rates. Lenders also factor in council tax, utilities, childcare and other regular commitments from your bank statements and credit file, not just formal debts.
Does a bigger deposit increase how much I can borrow?
Not the loan itself — the LTI and stress limits apply to the amount borrowed, and a deposit simply adds to the price you can reach. Indirectly it helps: a bigger deposit usually unlocks cheaper rates (lower loan-to-value bands), and a cheaper pay rate means a cheaper stressed rate too, which raises the stress-test limit.
What formula does this uk mortgage affordability calculator use?
LTI loan = gross income × multiple. Stress loan = the loan whose payment at (pay rate + stress margin) exactly equals your monthly budget: Loan = B × (1 − (1 + s)^−n) ÷ s, where B is the monthly budget after commitments, s the monthly stressed rate and n the months in the term. Max mortgage = min(LTI loan, stress loan). The stress loan inverts the standard repayment formula M = P × r(1 + r)^n ÷ ((1 + r)^n − 1): instead of solving for the payment M given a loan P, it solves for the largest P whose stressed payment fits the budget B. The budget itself is (gross income ÷ 12 × budget share) − committed monthly outgoings. The worked example on this page applies the formula step by step with real numbers, so you can verify the result by hand.