Mortgage stress test calculator
Your payment at the rate lenders actually test — not the one advertised.
Lenders no longer apply one fixed FCA stress formula, but most still check you could cope if rates rose a few points above your deal — this is that test, using a 35% payment-to-income yardstick. Illustration only, not financial advice — affordability checks also weigh your outgoings, debts and credit history.
Lenders do not check whether you can afford the advertised rate — they check whether you could still pay if rates rose. Under FCA affordability rules, most lenders test your payment at a stressed rate: typically the rate you would roll onto after the deal ends plus a margin of at least 1 percentage point, which in practice often lands several points above the rate you will actually pay. Fix for 5 years or more and many lenders stress at (or near) the actual product rate, which is one quiet reason longer fixes can unlock bigger loans.
The arithmetic bites. A £200,000 loan over 25 years costs about £1,112 a month at 4.5% — but stressed at 8% the test payment is roughly £1,544. If your income and outgoings cannot absorb the stressed figure, the lender shrinks the loan until they can, regardless of the income multiple. This is usually what is happening when someone who comfortably pays £1,300 in rent is declined for a mortgage costing £1,100: the tenancy is judged on today’s rent, the mortgage on a hypothetical worse future.
The test protects you as well as the lender — plenty of borrowers who fixed at under 2% before 2022 discovered exactly what the stress test was for when they re-fixed above 5%. Use the calculator the same way: if the stressed payment would genuinely break your budget, the loan is too big even if a lender will grant it. Note the Bank of England’s separate blanket 3-point stress rule was withdrawn in 2022; what remains is each lender’s own FCA-governed test, so outcomes vary between lenders.
Common questions
What rate do lenders stress test at?
Most commonly the lender’s reversion rate (the standard variable rate you’d roll onto) plus at least 1 percentage point — often 8–9% when SVRs are high, even if your fix is under 5%. Deals fixed for 5+ years are frequently stressed at a lower rate, sometimes the product rate itself. Each lender sets its own figure.
Why was I offered less than 4.5 times my salary?
Because the stress test binds before the income multiple does. Committed outgoings — childcare, car finance, loans — reduce the surplus available to meet a stressed payment, so the affordable loan shrinks. Two households with identical salaries routinely get offers tens of thousands of pounds apart for this reason.
I pay more in rent than the mortgage would cost. Why might I still fail?
The lender is not testing today’s payment — they are testing a payment at perhaps 8%, plus your other outgoings, against regulated affordability rules. Rent history helps evidence reliability (and a few lenders now weigh it explicitly), but it does not switch the stress test off.
How can I improve my stress test result?
Reduce committed monthly outgoings before applying (clearing car finance or card balances helps most), consider a 5-year-plus fix which is often stressed more gently, extend the term to lower the tested payment, or bring a bigger deposit. A broker can also route you to lenders whose stress models suit your case — they genuinely differ.
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