Most UK lenders cap your borrowing at 4 to 4.5 times annual gross household income, with a smaller number stretching to 5×. That multiple is then trimmed by existing monthly debts, and stress-tested against a higher rate to make sure you can still afford the mortgage if rates rise. Your deposit doesn't change the income multiple — but it does change the rate you're offered, which feeds into the same affordability math.

The two rules every UK lender runs

Two affordability tests sit behind almost every mortgage decision:

• Loan-to-income (LTI). The headline cap. Bank of England rules require lenders to keep no more than 15% of their new mortgage book at an LTI above 4.5×. That's why most products top out at 4.5× household income. Some lenders offer 4× as a default; a few stretch to 5× for higher earners.
• Debt-to-income (DTI). The supporting test. Your projected mortgage payment plus existing monthly commitments must stay below roughly 40–45% of net pay. Lenders convert this into a haircut on the LTI figure — typically reducing borrowing by ~£4,000 for every £100/month of existing debt.

Use the affordability calculator to apply both rules at your income, commitments and deposit.

What 4×, 4.5× and 5× look like in pounds

Annual gross income	Conservative (4×)	Standard (4.5×)	Stretch (5×)
£25,000	£100,000	£112,500	£125,000
£35,000	£140,000	£157,500	£175,000
£45,000	£180,000	£202,500	£225,000
£60,000	£240,000	£270,000	£300,000
£75,000	£300,000	£337,500	£375,000
£90,000	£360,000	£405,000	£450,000
£120,000	£480,000	£540,000	£600,000

Headline borrowing only — before debt haircuts and stress testing. For joint applications, add both gross incomes together and apply the multiple to the combined figure.

How monthly debts cut your borrowing

Lenders treat every £100 of monthly committed debt as a £4,000 reduction in borrowing capacity. The logic: that £100 has to come from the same income that would otherwise support mortgage payments, so the available capacity is smaller.

Worked example. Household income £60,000, standard 4.5× multiple:

• Headline: 60,000 × 4.5 = £270,000
• £200/month car finance: −£8,000 → £262,000
• £300/month credit card minimums: −£12,000 → £250,000
• £150/month student loan: −£6,000 → £244,000

So £650/month of commitments shaves the £270,000 headline figure to £244,000 — a 10% reduction. Lender-specific models vary, but the rule of thumb is reliable enough for planning.

What counts as "monthly commitments"

Lenders include almost all regular committed outgoings in the DTI test:

• Loans and finance: personal loans, car finance (HP or PCP), furniture finance, BNPL (Klarna, Clearpay, etc).
• Credit card minimum payments: typically 3–5% of the balance, not the actual usage. Pay balances down before applying.
• Student loans: usually deducted from net income. Plan 2/4/5 vs Plan 1 makes a small difference depending on lender.
• Child maintenance: fully counted.
• Council tax, utilities, broadband, subscriptions: not counted as commitments, but lenders look at your bank statements for spending patterns. Persistent overdraft use or recurring high subscription spend can affect the underwriter's view.

Joint vs single applications

For a joint mortgage, lenders apply the income multiple to combined household gross income. Some practical points:

• Adding a low earner. Adding a second income of £15,000 to a £50,000 sole income lifts the headline 4.5× borrowing from £225,000 to £292,500 — a £67,500 increase.
• Adding a partner with debt. Their commitments get added to yours for the DTI test. If they have £400/month of finance payments, that's a £16,000 cut to the joint capacity.
• Both must be on the deeds. Lenders generally require all named applicants to be named owners. If only one will be on the deeds, the mortgage is a sole application using that person's income alone.
• Joint liability. Both applicants are jointly and severally liable for the full mortgage. If one falls behind, the other is responsible for the whole amount.

What the stress test means in 2026

Since 2014, FCA rules have required lenders to check that borrowers could still afford their mortgage if rates rose. The original "3 percentage points above pay rate" test was formally withdrawn in August 2022, but lenders didn't drop stress testing — they replaced it with their own internal versions. The typical bank now stress-tests at either:

• Standard variable rate (SVR) + 1% — usually 7–9% in the current environment.
• A flat benchmark — often 7% or 8%.

Whichever is higher applies. Use the mortgage stress test calculator to see what your payment would look like at +1, +2 and +3 percentage points.

What else lenders look at

The LTI figure is the starting point, not the offer. Other inputs:

• Credit file. Missed payments, defaults, CCJs and recent credit applications in the last 6 years all narrow product choice and may reduce LTI capacity.
• Employment type. Permanent PAYE is treated most favourably. Self-employed typically need 2–3 years of accounts. Contractors are assessed on day rate × 5 × 46–48 weeks. Probation usually requires written confirmation of permanent status.
• Variable income. Bonus, commission, overtime, second-job income — usually averaged across 2 years, often discounted (50–75%).
• Term length and age. Most lenders need the mortgage to end before age 70–75. Borrowers in their 40s+ have less term flexibility.
• Property type. Ex-local-authority, flats above commercial premises, short leaseholds (under 80 years) and non-standard construction all narrow your lender choice.

Affordability killers — common surprises

• Recent BNPL activity. Klarna and Clearpay now appear on credit files and count toward the DTI haircut.
• Persistent overdraft use. Sitting in your overdraft in the 3 months before application is a common decline reason.
• Probation period. Most lenders prefer you to be out of probation. A handful accept it with a written permanent-status letter.
• Frequent address changes. 3+ moves in the last 3 years adds underwriting friction and can delay the offer.
• Unexplained large credits. Anything over ~£1,000 hitting your account in the 3 months before application needs a clear paper trail.

Borrowing isn't the same as affordability

The mortgage you can get is rarely the mortgage you should take. The headline capacity assumes the lender's view of risk; your own view of comfort might be tighter. A useful sanity check: at the standard 4.5× scenario, what does the monthly payment look like as a percentage of net household income?

• Under 30% of gross — comfortable.
• 30–40% of gross — manageable, leaves moderate headroom.
• 40–50% of gross — stretched. Most lenders will fund this but it leaves limited buffer.
• Over 50% of gross — high risk. Expect declines unless other factors compensate.

Run your own numbers on the affordability calculator — it shows the payment-to-income band for each scenario.

Frequently asked questions

How much mortgage can I afford on £30,000 income?

At the standard 4.5× loan-to-income multiple, a single applicant on £30,000 gross can typically borrow around £135,000 before any debt adjustment. Joint applicants on £30,000 each can borrow around £270,000 combined at 4.5×. Existing monthly debt commitments reduce that figure by roughly £4,000 per £100/month of payments.

How much mortgage can I afford on £50,000 income?

At 4.5× household income, a single applicant on £50,000 can typically borrow around £225,000. A higher-earner stretch to 5× — available on selected lenders — gives £250,000. Add a deposit of 10–25% to see your maximum property price.

What's the typical UK income multiple?

4.5× household gross income is the most common headline multiple. Some lenders default to 4× for thinner credit files or specific income types. A limited number stretch to 5× for higher earners (typically £75,000+ individual) or professionals with predictable income growth such as doctors, lawyers and accountants.

Do monthly debts really cut what I can borrow?

Yes — materially. The standard rule of thumb is every £100 of monthly debt payments reduces your headline borrowing by around £4,000. A £400/month car finance payment cuts a £350,000 mortgage to around £334,000 before any other adjustments. Pay down small commitments before applying if possible.

Does student loan count as a monthly commitment?

Yes — most UK lenders deduct your student loan repayment from net income when assessing affordability. The impact is gentler than for consumer debt, but a £200/month student loan can shave £6,000–£10,000 off your maximum mortgage depending on the lender's model.

How does a joint mortgage change affordability?

For a joint mortgage, lenders apply the income multiple to combined household gross income. Two applicants on £40,000 each can typically borrow around £360,000 at the standard 4.5× — the same as one applicant on £80,000, before commitments. Both incomes must be verifiable; both applicants share liability for the loan.

What is the FCA stress test now?

The original FCA 3-percentage-point stress test was withdrawn in August 2022, but lenders still run internal stress tests before issuing an offer. The typical lender test is the standard variable rate plus 1%, or a flat 7–8% benchmark — whichever is higher. The test checks you could still afford the mortgage if rates rose materially.

Related calculators

Related guides

To understand exactly how your take-home pay supports your mortgage, PayslipCheck breaks down a UK payslip line by line. For self-employed income evidence, Freelance Toolkit UK covers SA302s and tax-year overviews.

Last reviewed: 24 May 2026.